I told my friend to delete all of these apps (mistake)

Alright, I need some help understanding what the hell happened here.

For context, my friend called me one day because he was having an issue with his PC. Whenever he tried to open the NVIDIA app, the actual app window wouldn’t open. It would show up minimized on the taskbar, but clicking it did nothing. The window never actually appeared.

I told him to uninstall all the NVIDIA apps/drivers and reinstall everything.

The only reason I told him that is because I’ve done the same thing on my own PC before and nothing bad happened.

But after he did it, his desktop icons started bugging out and disappearing. Then he restarted the PC, and after that it wouldn’t go past the motherboard logo. It would just black screen.

We tried hard restarting it 2–3 times by holding the power button to try to force Windows into recovery mode, but that didn’t work. We tried getting into BIOS and launching Windows in safe mode, but that didn’t work either. System restore also didn’t work.

Basically, we couldn’t get it past the black screen no matter what we tried.

After 1–2 hours of troubleshooting, we gave up and he took it to Micro Center.

The guys at Micro Center said the issue may have been connected to the fact that a few months ago, he upgraded from a 4070 build to a 5090 build with mostly new parts, but kept the same M.2 drive from the old build and moved it into the new one without formatting Windows or doing a clean install.

They said because of that, the NVIDIA SDKs, Graphics Driver, and PhysX System Software from the old setup were not supposed to be removed the way he removed them.

They also said the motherboard may have gotten corrupted somehow. They tried clearing the CMOS by removing/reinserting the motherboard battery, and they also tried resetting it by shorting the reset pins/jumper with a screwdriver, but that didn’t fix anything.

In the end, they formatted all of his storage, replaced the motherboard, and now everything works again.

The part I’m confused about is this:

Was this really caused by moving the old M.2 drive from the 4070 build into the new 5090 build without doing a clean Windows install?

Did old NVIDIA/driver stuff from the previous build somehow mess with the NVIDIA app or drivers months later?

Could deleting NVIDIA SDKs / Graphics Driver / PhysX actually brick Windows this badly?

Or is it more likely that Windows got corrupted, and the motherboard replacement was just Micro Center being extra cautious?

Because from my side, uninstalling NVIDIA software and reinstalling drivers should not cook an entire PC.

Anyone have any idea what actually happened here?