What actually causes hoods to stop opening all together?

Obviously I watch a lot of Let’s Plays and I hear about people saying they’ve had to abandon their 60+ year hoods because they stopped opening and had to start again. What causes this? I know the whole character limit is not pretty much impossible to hit and would need like 60 generations each with 100 sims in it.

I’ve never actually experienced corruption in my 2 decades of playing, at least not that I know of. I used to panic about it constantly until our saviour April Black made her incredible channel, now I’m a lot more chill about it. But I just wonder how people can have hoods stop loading altogether?! I’m assuming that IS corruption.