I don't know why you think accepting cryptocurrencies is different from "accepting any money from businesses".

Without business funding, presidential campaigns would have much less money. There are countries like France where business donations indeed are banned, but in many it is seen as "normal". And if some business from "industry X" donates to a candidate, then often there is obviously an expectation that this may help the business, e.g. via "friendly" regulations.

I think however if Ripple expects "help" in the specific case of the SEC against them, that may be indeed illegal and a corruption case. However, it would be completely legal if the Congress after the election creates or changes legislation so it's friendly to Ripple. This is probably the intention of the donations: to create a friendly environment for the own lobbyists.

By the way, the president can't appoint the SEC chair on its own, he needs consent of the Senate. And he can't "fire" a chair while their mandate is still running.