Remember that Tweet from his first election saying how he is not a fan of cryptocurrencies. And then years later he has a complete change of heart.
So most likely his kids started to learn about crypto, invested tons of money into it, then told him about what is so great about crypto and he knew that if he was pro bitcoin then it would be good for their investment. Either way its impossible to prove.
I was thinking originally that he is pro bitcoin just to get more votes from all the crypto holders. Didnt think it was because his family had a huge stake in it. Either way, we can see that crypto regulations will be loose until the next administration at least and its good for crypto.
I think that Trump knows how to pander to the media. Give them what they want. True, in his first tenure, he was reluctant to support crypto currencies and I'm sure by then he didn't have any holdings but come his second tenure, he saw it as not just a means to sway the Bitcoin community, but also as a means to further grow his wealth. You have a point that with him supporting crypto, it would make for a loose form of regulation but what if he becomes hooked on favoring his token more than he does for Bitcoin? Just a thought.