Perhaps that's part of it but I think a bigger reason is because Kanye lost a lot of money and believes helping Trump is the best way to recover. Yea Kanye is "rich" but he's also in debt, and if not for his wife he'd truly be fukked. He needs capital and I think there's a tacit agreement that if he can move enough black people into Trump's camp, he will be rewarded. And I think it's a reason why his wife keeps "freeing" random black people with the help of Trump.
And I think the other thing is that Trump's entire persona and campaign was fresh compared to Hillary. The rallies, the marketing slogans...all that shyt was in Kanye's lane as an entertainer. Whereas Hillary was just the same shyt we've seen before, but just less popular/effective. Trump was Kanye's idea of what "subversive" is. And he's so far removed from the real world that he doesn't know or care about the consequences of Trump's policies. This is all abstract to him, and about general beliefs rather than people.