Backlight only working, not screen, what could it be?

I found a Switch on the street, water damaged and abandoned, which worked but the LCD didn’t, only backlight. The digitizer also works. Just bought a new LCD, to my dismay, it wasn’t the problem, and now I’m trying to figure out what is. I’ve seen many different things cause LCD failure online, and I’m trying to figure out what it could be. Other than the screen connectors itself, what else could it be?