re: Trump Trial: Judge Merchan won't allow certain Defense testimony

I just can't get over the defense not being able to have an expert witness to talk about the campaign finance crime - which is the entire reason the state is able to go after the "falsified business records" because it was supposedly done in furtherance of another crime. How can he not have an expert as a witness to say why he didn't commit a campaign finance crime? I'm at a loss for words.

ETA: I also don't remember the State using an expert to talk about campaign finance laws so essentially the judge is saying that since Trump was charged with that - nevermind the feds chose to not prosecute any alleged campaign finance crimes - it means he did it and is allowed no defense.