He's been talking about that for the past 7+ years. Have you missed it? Trump is being challenged by other Republicans. I think he has every right to vocalize his reasons why those other people aren't qualified. If he didn't do it to them, they will definitely do it to him.
Remember, it was the Hillary camp who started the rumors about Obama not being born here. It wasn't a Republican. So far, President Trump hasn't had to hire anyone to write a fake dossier on DeSantis or any of his other opponents...and somehow, I don't think he'd ever stoop that low. I'm just glad that lying, evil bastard died when he did. It didn't come soon enough.
Back in 2015, after Trump held a rally in Phoenix, Arizona, McCain was asked about it. He said that it was a very bad situation what Trump had done...that he had "fired up the crazies," simply because Trump had talked to the crowd about the problems with the southern border. Trump was asked a week later about McCain's comments, and he said that McCain needed to apologize to his supporters over that remark. He also made his famous "I like people who weren't captured" comment. You never heard about the comments McCain had made to start the McCain/Trump feud. All you heard was the media and the Democrat's claiming he was attacking a veteran. McCain even pulled some crap about push poll calls back when he was vying with Bush for the Presidential nomination. He claimed that one person got a call from Bush's camp who was making calls telling lies about him, yet when it was looked into, nobody seemed to be able to pinpoint the polling company that allegedly made "the" call, or the fact that any of Bush's polling companies were using a script that included any negative comments about McCain. And we know that McCain was knee-deep in the distribution of the fake dossier.
I've been reading some articles. From what I have read of Trump's comments, he never verbalized support for Disney. He said that DeSantis's feud with Disney could possibly destroy the economy of the State, and he has a right to say that. That's not taking Disney's side in the argument.