My rear derailleur hanger went yesterday on the commute home. Luckily it was as I started off again after a turn. Still managed to take out 2 spokes itself and possibly the derailleur itself. Luckily, I had spares back to my knackered old Shimano for now.
I’ve seen this happen many times because of riding downhill.
It’s not necessarily a misaligned derailleur. It will eventually happen to any bike because the derailleur hanger is made of sintered metal which will break easily. This saves your derailleur from more severe harm. Usually for road bikes this happens from age and natural vibrations. For us downhill bikers it’s usually from smacks against trees and rocks.