Can leveraged etfs go to zero without index being down 33%+?

I’m trying to understand potential risks involved in leveraged ETFs like UPRO, TQQQ, TMF, etc. I understand that if the underlying index goes down by more than 33% then it’s worth 0 on 3x leverage. And that it’ll be down 99.9% in situations like the depression.

But what about other situations? What if Proshares or Direxion go bankrupt like so many of these crypto platforms right now? From what I can tell, most get their leverage by using swaps??is there a way for these swaps to have a breakdown and UPRO to go to zero without the SP500 going down 33%?

I’m trying to understand all the risks involved apart from the obvious ones. My main concern is if SP500 is only down 10% on a single day, but something breaks and UPRO goes down 90%+. If there are any risks you can think of that would cause a leveraged ETF to drop without the underlying index dropping in the appropriate amount, please comment below