For the same people accept Tether's claims of solvency even though they refuse audits and obviously lie about ownership of various assets. For the same reason people ignore wash trading. For the same reason people continue using Sam-coins even after FTX's implosion.

Because A) they're not paying attention, B) they're in denial and C) because they think they can profit in the short term before it collapses, or that the odds are in their favor to profit despite the risks.

People will accept it as long as it mostly operates in an expected manner and they get their payout.

People are very good at convincing themselves that because something has not happened, therefore it will not.

When UMA is eventually abused to make a lot of money, then perhaps things will change.