Interesting thought: Anyone who has a potential suit against Trump should go for it. As long as they can force Trump to testify under oath, they will win a large settlement before the trial. The amount could be astronomical, because Trump's lawyers know testimony under oath would result in perjury charges. So they will settle for any amount necessary to avoid that.
He can't testify, because he can't help but perjure himself. He really can't tell fact from fiction, as evidenced by his thousands of lies. He hardly bothers to make public statements or tweets unless it is to lie! That should be the reason for an Amendment 25 action, if the people around him had any integrity. But of course there was a reason he hand-picked such ethically-challenged slugs for cabinet and VP posts.