Can a water pump pulley with bearing play cause the serpentine belt to come off (belt is also 350.000KM old)?

I have my friend's Ford Falcon with over 350,000KM have its belt come off from the power steering pump, idler pulley, belt tensioner, power steering, crankshaft pulley, and AC compressor while it was in motion. But can one pulley with bearing play cause the serpentine belt to slip off?

It has over 350.000KM and the belt was never replaced. It's water pump had also started to leak when the belt came off.

Here's the video showing the belt and how it's supposed to go on or around the pulleys. I think it is a serpentine belt, not a V-belt.

Added (1). My guess is that the pulley with the bearing play from the water [ump had gone to an angle that caused the belt to jump right off the water pump pulley and some other pulleys. But why would the water pump develop a leak at the same time the belt jumped off the water pump?

The water pump is leaking so it has to be replaced. The belt has never been replaced since new? I doubt it but if it is true, then it really needs to be replaced. Replace the tensioner too. See if that fixes the issue. Troubleshoot further if you do not have a fix.

Think like a mechanic. Do not overthink it.

Yes. A pulley on a serpentine belt has to be lined up with it. If it is at an angle the belt can be thrown off. This happens when a bearing in a water pump goes bad. Often you can tell something is wrong because you hear a funny ticking coming from the car engine area. Another problem that might happen is if the fan is directly attached to the water pump pulley, as the pulley goes off line the fan can go thru the radiator. That is fun.

Yeah a waterpump either fails when the bearing goes or if the gasket goes… When the bearing goes it starts to wobble and no longer revolves in 1 set place… So if your waterpump is in a dependant place on your aux belt it'll throw it off… My waterpump bearing went & because it wasn't part of the main serpentine system it didn't lose the belt… Yours should probably be changed… But once changed check that all the pulleys are straight and get a flat ruler to make sure everything's in the right place

YES

YES
The belt does not last FOREVER.
They get worn and need to be replaced at some point.

The "pulley". Bearings, wheels and other stuff connected along the belt also wear out and need to be replaced/repaired as necessary.

Don't drive it with a leaking water pump. The water pump can suddenly fail totally and besides over heating your motor when the coolant all pumps out of the cooling system you'll also end up with a $150 or more tow truck bill. With the serpentine belt off spin all the pulleys by hank to feel for dry bearings and to see if the bearings have play. Always put a 50/50 antifreeze and water mixture back in the cooling system. Failing to use antifreeze will cause the water pump seal to go bad and the inside of the motor rusts up and causes the heater core and radiator to get plugged up.

Yes.

Yes
belts run to the highest point so if a pulley is misaligned then it will rty to align itself and therefore run of the pulley

Yes cause the pulley is moving up and down when it's post to be still