How do I fix the sizing of my grid cells?

I'm trying to replicate this website https://rickandmortyapi.com/ I'm making my version more responsive by using grid layouts. When I set the grid-template-columns to repeat(auto-fit, minmax(589.19, 1fr)) the grid cells extend horizontally to the end of the page despite me setting the minmax. The reason I did this is to have the number of cells per row change depending on the size of the browser window.

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

const mainEl = document.querySelector("main");

const main = async () => {
  const characters = await fetchAllCharacters();
  const maxCells = 6;

  for (let i = 0; i < Math.min(characters.length, maxCells); i++) {
    const character = characters[i];
    const episode = await fetchJsonAsync(character.episode[0]);
    mainEl.insertAdjacentHTML('beforeend', renderCharacterHTML(character, episode));
  }
};

const renderCharacterHTML = (character, episode) => `
  <article class="character-card">
    <div class="image-container">
      <img src="${character.image}" alt="Character" height="100%" width="100%">
    </div>
    <div class="character-info">
      <div class="section">
        <h2 class="orangefy">${character.name}</h2>
        <div class="status">
          <span class="status-dot ${getStatusColor(character.status)}"></span>
          <span class="status">${character.status} - ${character.species}</span>
        </div>
      </div>
      <div class="section">
        <span class="greytext">Last known location:</span>
        <span class="orangefy">${character.location.name}</span>
      </div>
      <div class="section">
        <span class="greytext">First seen in:</span>
        <span class="orangefy">${episode.name}</span>
      </div>
    </div>
  </article>
`;

const getStatusColor = (status) => {
  switch (status.toLowerCase()) {
    case 'unknown':
      return 'grey';
    case 'dead':
      return 'red';
    case 'alive':
      return 'green';
    default:
      return '';
  }
};

const fetchAllCharacters = async () => {
  const response = await fetchJsonAsync('https://rickandmortyapi.com/api/character');
  return response.results;
};

const fetchJsonAsync = async (url) => {
  try {
    let response = await fetch(url);
    if (!response.ok) throw new Error(response.statusText);
    return response.json();
  } catch (err) {
    console.error('Error fetching JSON:', err);
  }
};

main();

<!-- language: lang-css -->

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
}

.top-container{
    position: relative;
    height: 465px;
    padding-bottom: 0;
}

.showcase {
    background-color: rgb(39,43,51);

}

.showcase-inner {
    margin: 0;
    padding-top: 80px;
    padding-bottom: 80px;
    padding-left: 10px;
    padding-right: 10px;
}

.footer { 
    background-color: rgb(32,35,41);
    padding-top: 50px;
    padding-bottom: 21px;
}

h1{
    font-size: 100px;
    text-align: center;
    font-weight: 1000;
    color: rgb(32,35,41);
}

h2{
    font-weight: 1000;
    font-size: x-larges;
}


main {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(589.19, 1fr));
    gap: 0;
    overflow-x: hidden;
}

.image-container{
    display: flex;
}

.image-container img{
    width: 229.2px;
    height: 220px;
    border-radius: 10px 0px 0px 10px;     
}


article{
    margin-left: 5px;
    margin-right: 5px;
}


.character-card{
    display: flex;
    margin: 13.5px;
    background-color: rgb(60,62,68);
    border-radius: 10px;
    box-shadow: 0 0 10px rgba(37, 37, 37, 0.5);
}

.character-info{
    display: flex;
    flex-direction: column;
    padding: 13.5px;
    position: relative;
}

.section{
    display: flex;
    flex-direction: column;
    width: 330px;
    height: 64.33px;
    color: rgb(245,245,245);
}

.greytext{
    color: rgb(158,158,158);
    padding-top: 5px;
    padding-bottom: 10px;
}

.navbar {
    background-color: #ffffff;
    list-style-type: none;
    margin: 0;
    padding: 0;
    overflow: hidden;
    display: flex;
    justify-content: space-between;
}

.navbar li {
    float: left;
}

.navbar li a {
    display: block;
    color: #333;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
    transition: color 0.2s;
}

.content-links{
    margin-left: auto;
    padding: 10px;
    margin-right: 10px;
    font-size: 20px;
    font-weight: 750;
}

.content-links a:hover{
    color: rgb(255,152,0);
}

.homebutton{
    margin-right: auto;
}

.homebutton img{
    width: 50px;
    height: 50px;
}

.status {
    display: flex;
    align-items: center;
    font-weight: 600;
}

.status-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    display: inline-block;
    margin-right: 5px;
}
  
.status-dot.grey {
    background-color: rgb(158,158,158);
}
  
.status-dot.red {
    background-color: rgb(214,61,46);
}
  
.status-dot.green {
    background-color: rgb(85,204,68);
}
  
.about-content{
    display: flex;
    flex-direction: column;
    padding: 5px;
    padding-bottom: 100px;
    margin-left: 500px;
    margin-right: 500px;
    font-size: 110%;
    color: rgb(66,66,66);
}

.abouth2 {
    font-size: 35px;
    font-weight: 800;
    margin-bottom: 30px;
    color: rgb(32,35,41);
}

.abouth3 {
    font-size: 25px;
    font-weight: 800;
    margin-top: 10px;
    margin-bottom: 10px;
    color: rgb(32,35,41);
}

.ablink {
    text-decoration-color: rgb(255,152,0);
    text-decoration-thickness: 2px;
    text-underline-offset: 4px;
    color: rgb(66,66,66);
}

.ablink:hover {
    text-decoration: none;
    color: rgb(255,152,0);
    transition: color 0.2s;
}

.footer-info {
    display: flex;
    justify-content: center;
    list-style: none;
    padding-top: 40px;
    margin: 0;
    font-size: 14px;
    font-weight: 750;
    color: rgb(158, 158, 158);
}

.footer-info li {
    margin-right: 20px;
}

.socials {
    display: flex;
    justify-content: center;
    align-items: center;
    padding-top: 2px;
    padding-bottom: 2px;
}

.socials a {
    margin: 14px;
}

.socials a:hover svg path {
    fill: rgb(255, 152, 0);
}

.sign {
    color: rgb(158, 158, 158);
    text-align: center;
    font-size: 13px;
    padding-top: 15px;
    padding-bottom: 50px;
}

.footer-link {
    color:rgb(255, 255, 255);
    font-weight: 700;
    text-decoration-color: rgb(255,152,0);
    text-decoration-thickness: 2px;
    text-underline-offset: 4px;

}

.footer-link:hover {
    text-decoration: none;
    color: rgb(255,152,0);
    transition: color 0.2s;
}

.banner {
    position: absolute;
    left: 50%;
    transform: translateX(-50%);
    bottom: 0;
  }
  
  .banner svg {
    width: 480px; 
    height: auto;
  }

.banner-text{
    display: flex; 
    justify-content: center;
    align-items:center;
    z-index: 10;
    position: relative;
    top: 150px;
  }

.poweredby {
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    padding-top: 30px;
}

.poweredby-icon {
    padding-left: 18px;
    padding-right: 18px;
}

.server-status {
    display: flex;
    align-items: center;
    text-justify: center;
    justify-content: center;
    font-weight: 700;
    font-size: 14px;
    padding-top: 10px;
}

.server-status-dot {
    display: inline-block;
    width: 9px;
    height: 9px;
    border-radius: 50%;
    background-color: rgb(85,204,68);
    margin-left: 10px;
}

.status-link {
    text-decoration: none;
    color: rgb(158, 158, 158);
}

.status-link:hover {
    color: rgb(255,152,0);
    transition: color 0.2s;
}

.orangefy:hover {
    color: rgb(255,152,0);

}

<!-- language: lang-html -->

<!DOCTYPE html>
<html lang="en">
    <head>
        <title>Rick and Morty API</title>
        <meta charset="UTF-8">
        <link rel="stylesheet" href="style.css">
    </head>

    <body>
        <ul class="navbar">
            <li class="homebutton"><a href="landing.html"><img src="RMAPI-homepagebutton.png" alt="Home"></a></li>
            <li class="content-links"><a href="about.html">About</a></li>
        </ul>
        <div class="top-container">
            <h1 class="banner-text">The Rick and Morty API</h1>
        </div>
        <div class="showcase">
            <div class="showcase-inner">
                <main></main>
            </div>
        </div>
        <script src="script.js"></script>
    </body>
</html>

<!-- end snippet -->

here I have checked your grid-template-columns css is not applying in tag main.
I have tried and made some changes in css for main class which is giving desired output.

main {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(589px, 1fr));
    gap: 0;
    overflow-x: hidden;
}

May be It will help you... Thank you...!