Android displays two recyclerViews after I rotate the screen

I keep a fragment in a FrameLayout. In the fragment I use recycler view. It works fine, the only thing is that when I rotate the phone I see two recycler views, one on another (The second recycler is just in the background though, it's like a picture and I can neither scroll it, nor to click on its items). It still works fine, I can manipulate the new recycler with no problem. But this is what happens when I scroll down:

CrimeListFragment.class which contains the Recycler:

public class CrimeListFragment extends Fragment {

    private FragmentCrimeLabBinding binding;

    private static final int REQUEST_CRIME = 1;

    private RecyclerView.Adapter mAdapter;

    private int position;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView (LayoutInflater inflater,
                              ViewGroup container,
                              Bundle savedInstanceState) {
        binding = FragmentCrimeLabBinding.inflate(inflater, container, false);
        View view = binding.getRoot();

        binding.rvCrimeList.setLayoutManager(new LinearLayoutManager(view.getContext()));
        binding.rvCrimeList.hasFixedSize();
        mAdapter = new MyAdapter(CrimeLab.getInstance(getActivity()).getCrimes(), getActivity());
        binding.rvCrimeList.setAdapter(mAdapter);
        return view;
    }

    @Override
    public void onResume() {
        updateUI();
        super.onResume();
    }

    private void updateUI() {
        CrimeLab crimeLab = CrimeLab.getInstance(getActivity());
        List<Crime> crimes = crimeLab.getCrimes();

        if (mAdapter == null) {
            mAdapter = new MyAdapter(crimes,getActivity());
            binding.rvCrimeList.setAdapter(mAdapter);
        } else {
            mAdapter.notifyDataSetChanged();
        }
    }


    @Override
    public void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        if(requestCode == REQUEST_CRIME) {
            if(resultCode == Activity.RESULT_OK) {
                position = data.getIntExtra("Position",-1);
                updateUI();
            }
        }
    }
}

CrimeListActivity contains the fragment:

public class CrimeListActivity extends AppCompatActivity {
    ActivityCrimeLabBinding binding;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        binding = ActivityCrimeLabBinding.inflate(getLayoutInflater());
        setContentView(binding.getRoot());

        FragmentManager fm = getSupportFragmentManager();
        FragmentTransaction transaction = fm.beginTransaction();
        transaction.add(R.id.frame_layout, new CrimeListFragment()).commit();
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
    }
}

UPD: I found the solution right after I published the question.
In the Activity.onCreate() I called fragmentTransaction.add() method. Instead, I call .replace() and now it works as I expect.
But the question is still not resolved, because I have no idea why it works like this. Why my fragment is not removed after rotation by default? Why should I call methods such as detach() or replace()? It differs with activities (e.g. when we rotate the screen, an activity is destroyed by android altogether )

Rotating the device triggers a configuration change and your activity is recreated. By not checking if saved state is null, you end up adding multiple fragments. Change your code to this:

if (savedInstanceState == null){
FragmentManager fm = getSupportFragmentManager();
    FragmentTransaction transaction = 
fm.beginTransaction();
    transaction.add(R.id.frame_layout, new 
CrimeListFragment()).commit();}

Add this line to your manifest, where you define your activity:

<activity android:configChanges="orientation|screenSize">
       
</activity>

This prevents the OS from recreating the activity at rotation, which leads in issues like yours.