Fully functional display, but only for Samsung boot screen

Why would a Samsung Galaxy A51 be fully functional, but display absolutely nothing on the screen EXCEPT for the startup logo, recovery menu and the charging animation when the phone is switched off?

Got someone's phone where the display stopped working a few months ago, except for the three cases as mentioned above. They factory resetted it at some company.

Went through the painful process of switching on TalkBack and doing the startup wizard, switching on USB debugging in settings, then connecting the command line tool "scrcpy" and being able to fully view the screen on my Macbook.

Now how would I go about restoring this phone's display on its own, rather than just operating it through my Macbook, given that the display works during the very start of the boot cycle as mentioned above?

Thanks!