I think there are many reasons that they decide to talk badly about it. Some like Warren Buffett send mixed messages - throughout his whole investing career he has repeatedly stayed clear of technology stocks and has admitted that he should have invested in many companies in that sector. He might want to help people avoid losing their money in a highly volatile asset like Bitcoin which comes from a good place, but it's hard to judge the opinion of a self proclaimed technophobe. Trump is another story entirely and will bend whichever way the wind blows if he thought he could use it to his advantage, if there was money to be made in Bitcoin by easy manipulation which would not interfere with his new found political career then he would certainly take that path.