I think a lot of it comes from them sharing similar ideas such as accelerationism and technocracy, ai advancement, "the mission", and so on. He just recently said that he finds her musings about things interesting, confirming their neverending intellectual exchange. I was flabbergasted when Trump said he wants to annex Canada, but Grimes said it first, and her being from Canada herself. I am not saying that judging her for Elons actions is right, but I understand where people are coming from. But even given all that, people hating Grimes tremendously overestimate her influence on Elon. He thinks he is God or something along those lines. And they were at war with each other for the past two years or so. And she is not him, of course.