I don't think this is a tactic to help Trump get more clearance votes expressing his positive views in favor of bitcoin. Remember that those in power will do what they feel is in the best interest of the country first, and if things do not get a positive economic balance then it will be a good idea to turn your back on things. It's not surprising that he declared it
But it's really nice that he is expressing a positive opinion on bitcoin, I remember he also expressed before that bitcoin is really harmful to the US economy

when he was still in office President, maybe that information is wrong but I don't pay too much attention. Because really, with bitcoin, it exists without too much influence on someone's judgment, support/opposition, bitcoin will still exist and develop.
Trump is on a crusade to win back the presidency of the United States, anything he says has as a purpose to gain voters, and even if for some reason this was not true, this is the only way we can interpret his actions as he is in the middle of a campaign.
Trump’s team probably realized there is a set of voters which may like a more liberal stance of the federal government towards bitcoin, and speaking to them in this way may gain him some valuable votes, but do I think Trump has really changed his stance and we may expect some positive news in the case he won? Absolutely not, and if he did I will be surprised it happened.