Why is onSaveInstanceState not called when the fragment is changed?

Question

Android

This is how I change the snippet

ProjectPage frag1;//ссылка на фрагмент
                FragmentTransaction fTrans;//ссылка на транзакции
                frag1 = new ProjectPage();//создание объекта фрагмента
                fTrans = getActivity().getSupportFragmentManager().beginTransaction();
                Bundle args = new Bundle();
                save_state_bundle(args);
                frag1.setArguments(args);
                fTrans.replace(R.id.main_layout, frag1);
                fTrans.addToBackStack(null);
                fTrans.commit();

But this does not call the onSaveInstanceState method. However, when returning to the fragment, filled EditTexts retain their state.
Also, the life cycle of the fragment comes to onDestroyView. But does not call onDestroy and onDetach.
And on return, onCreateView, onStart, onResume are called.
As I understand it, the fragment itself is not destroyed, but only its view is destroyed, but then why is its state partially restored if the onSaveInstanceState method was not called?
And yet, as I understand from the documentation, if there is not enough memory, the fragment itself can be deleted, even without calling onDestroy and onDetach, where then to store the state of the fragment?