This seems to be a core argument for those in opposition to shareholders getting liquidated bank assets vs depositors, but I don't really understand it because

This seems to be a core argument for those in opposition to shareholders getting liquidated bank assets vs depositors, but I don't really understand it because it seems to be kind of arbitrary. So there's fdic insurance, that's nice, but why does that mean anything regarding whether depositors or investors should be made whole first? The more important and real question is which option has what outcomes in terms of future investor behavior, or future depositor behavior? If it's a question of rigid legality that also doesn't make sense to me, because from what I remember from 2008 was the government's legal options were incredibly widespread.