If when you do so, you also have the intent to further or conceal another criminal offense, then you have committed the felony crime.
Exactly. The transactions in question violated campaign financing laws. It was claimed that Trump simply wanted to keep news of his liaison with Stormy from Melania, but that was obvious bullshit. He didn't want the public to find out about it, especially on top of the release of the Access Hollywood tape. And so he arranged to pay Stormy off. It was a campaign expense.