I'm not saying they should act in the majority's interest, I'm saying they should act in their own interest. Mitigate their risk by managing their capital properly instead of hoping ("Hope is a poor substitute for strategy") that things will work out. It's irrational to act in a way that, if a failure occurs, requires someone else to bail you out when they aren't legally or ethically required to bail you out. That's operating on hope, not strategy.

Putting all your capital in one too big to fail bank is the least costly option and the optimum strategy.

Until the US lets the largest bank fail this will continue to be the case.