This is all bullshit. Regardless whether Trump knew, there are no laws against paying hush money to someone.
The case isn’t about the hush money payments themselves. It’s strictly about how they were categorized in records - business vs. personal expenses. Mischaracterization of them is a misdemeanor, mischaracterization with the intent to commit another crime (unstated last I knew - campaign finance violation?) is a felony.
So they’d have to prove (I assume) mischaracterization, that Trump did it, that there was another crime, the mischaracterization was in an effort to commit this other crime, and that the state has the power to use a federal crime as the basis for this state statute.