Buffet has been screaming about how weird it is that he pays so little tax since forever, and he also started the initiative to get billionaires to donate all 99 % of their wealth when they die.
Just because you are rich doesn't mean that you only care about yourself, you can still love the nation as well.
As far as banks go, their bonus is connected to the state of the economy. Nearly every expert is saying that Trump would fukk up the economy so they are obviously rolling with the one who won't. I.e. they would rather take a higher income tax, which is being proposed by Hillary than a dude who wants to decrease taxes due to the high probability that he might fukk up the economy.