He knows it hurts him, and he doesn’t need to.
Others are challenging Cruz in court already,
and he no longer feels threatened by Cruz’s vote count.
Trump isn’t stupid.
It’s telling that so many people have to remind us that “Trump isn’t stupid.” Why do you suppose this comment is so often made? I believe it is because if he’s not stupid, the evidence is not clear to all who observe him. So it’s a counter intuitive conclusion. Most people hear the wild accusations, the inane bombast, the gratuitous insults, the vehement and contradictory statements (often contradicting himself), and conclude he’s stupid. Then, helpfully, a Trump supporter explains that we should all realize that Trump is not stupid. Thanks, it’s very reassuring to know that he’s not stupid.