Crypto isn't a scam, though lots of cryptocurrencies are scams. Don't buy crypto to try to get rich or even as an investment, get it if you want to buy stuff with it. Monero is a great cryptocurrency for that, and you can tell it's doing well by how many countries are threatened enough by it to make it harder to get (it has truly private transactions, just like cash).
I don't think he's doing any sort of pump and dump, he just wants crypto bros to vote for him. He tried courting libertarians at their convention (and rightfully got booed), and now he's courting crypto bros specifically (many libertarians are into crypto). He's just trying to expand his base a bit.