Why can't layout be changed? The background has changed, the views are not inserted?

Question

android studio

This is how the screen became:

I decided to make 2 layouts for different screen sizes, I created the layout-xxxhdpi folder,
copied the usual layout from the layout folder, and changed the background to green in it. I launched the emulator with a high resolution and the screen turned green, I think, okay, everything works as it should, I launch another emulator with a small screen, it is also green ... I decided to figure out why, deleted the layout-xxxhdpi folder, deleted it along with the layout, run again the emulator, again a green background, I go into the xml file and this is what is in it:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ui.view.fragments.MainFragment">
</androidx.constraintlayout.widget.ConstraintLayout>

There is no background in it, I think maybe I didn’t delete the folder, I go:

I go 10 more times, I check everything line by line.
I think it may not be shown here, I go to show in Explorer, there is nothing.
Okay, I decided to remove the background. Writes - it is used in other places.

But it is used as a background for mipmaps.
Fragments I switch through nav_graph, I go into it: I start

the emulator:

I press the button:

I create a button in fragment_main (activities in which the magic green background):
Writes in the logs:
E / AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.skeletmvp , PID: 2310
java.lang.NullPointerException: Missing required view with ID: com.example.skeletmvp:id/button2
at com.example.skeletmvp.databinding.FragmentMainBinding.bind(FragmentMainBinding.java:65)
at com.example.skeletmvp.databinding.FragmentMainBinding.inflate(FragmentMainBinding.java:47
) .MainFragment$bindingInflater$1.invoke(MainFragment.kt:12)
at com.example.skeletmvp.ui.view.fragments.MainFragment$bindingInflater$1.invoke(MainFragment.kt:10)
at com.example.skeletmvp.ui.view .fragments.BaseFragment.onCreateView(BaseFragment.kt:23)
at androidx.fragment.app.Fragment.performCreateView(Fragment.java:2698)
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:320)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1187)
at androidx.fragment.app.FragmentManager.addAddedFragments(FragmentManager.java:2224
) )
at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1953)
at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1849)
at androidx.fragment.app.FragmentManager$4.run(FragmentManager.java :413)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
pmagity....

The snippet is bare, all the code is hidden in the base snippet that I inherit from, I created a few more snippets, all work, in any I can create at least as many views, the background changes, I switched on the split screen, checked everything line by line several times, well, everything is the same as everywhere else, maybe I don’t see it, maybe you can see on the screenshots where the error is, why it happens ...