I don't know why people are acting like he won't...
This isn't taking the stand as a witness, this isn't presenting facts like a lawyer.
And his lawyers will still say everything they were gonna say anyways.
This is just trump knowing how much this will get his name out for something remotely positive. He isn't speaking to the judge, he's speaking to his followers. And this is going to bring in a shit ton of donations. He knows any sound bite is going all over national news for a day or two.
He can say whatever he wants and lie about whatever. And everyone has to listen to him, it's a captive audience of people that he believes hates him and are "witch hunting" him.
Well, sort of actually. A judge's main job is to make sure that a trial is fair and everyone sticks to the rules. And they have pretty wide latitude for enforcing that. I'd be pretty surprised if Trump was able to start blathering on about Hillary or stolen elections or whatever in that setting.