I think, the tweet has nothing to do with the dump that happened a few days ago.. I did see Bitcoin price touched $78k, and bounced and at the same time Trump wrote that... yes maybe the bounce was thanks to Trump's tweet, but I don't think Trump's goal was to save the Bitcoin market.. that was his ongoing political plan, and the BTC dump moment happened before the day Trump typed that...
Some people speculate that the BTC price dump to $78k was meant to happen, and it will go back up after that...
IMO, Trump's tweet only helped BTC above $90k, but the real price is in the $84k-$89k price range for now..