On the other hand, politicians tend to say exactly what the audience they are speaking to wants to hear, especially before elections. Election campaign promises are often not worth much.

Exactly this. Trump has a history of only saying what he thinks will get him elected and then completely changing his mind later. It will be no different here. He thinks being pro-crypto can get him elected, so that is what he says. Later if he is elected will be do what he said? Flip a coin and roll some dice and you have a better chance of being right than trying to predict if Trump will maintain a position from one day to the next.