Well he won the election and hid a story that could have yielded different results so personal gain in obvious. There is no doubt the payment was made and then covered up. So the only thing left is showing a directive by Trump. They shown that he was intimately involved with financial decisions with his business but have not tied him directly to hiding these funds.
My guess is that they are relying on Cohens testimony which is a weak case legally speaking. Practically speaking I think we all know that Trump slept with Stormy, continues to lie about it, paid to cover it up, and was well aware of everything that was being done.
But whether that gets proven in court is a different story. Personally I do think he did what he’s being accused of but also think the case is weak and very overblown. I don’t think it warrants jail time.