What made it a felony under New York law is the claim that the falsified records were intended to conceal another crime, specifically efforts to influence an election.
To a decent approximation, if Trump had not been running for office when he did this, then it wouldn't have been a crime. But then, he wouldn't have cared to cover it up.
Covering up that he got off with a porn star isn't the problem. Like Bill Clinton, it's the actual particulars of the coverup rather than generically that there was a desire to cover up an extramarital affair itself that's the problem.
Technically opening up your neighbor's mailbox is a felony. But in practice you will never be charged for it. Same thing with the hush money case. There is no law that makes covering up an affair illegal while running for office and Trump was not charged with any campaign finance violations. He was charged with the vague crime of "falsifying business records" which, while technically illegal in all cases, in practice is only ever charged if there is a victim who has been defrauded by the falsification. In this case there was none.
The Clinton case is exactly the same concept and is also 100% a politically motivated prosecution. So is the Hunter Biden gun charge. Nobody else ever would have been charged for that.