Musk decided that this is not what he voted for, nor what he supported and is now clearly playing with the idea of creating a rival party.
Not even his billions can match up against the two giant political parties. It’s allowed to have a new party in the US; there are the Reform Party, the Libertarian Party, and the Green Party, but these parties do not have a significant presence during elections.
It’s good that he parted ways with Trump and let him self-destruct, as it’s obvious that many of Trump’s decisions are affecting his business.
This is politics, and it's not Musk's game, and he still has four years to suffer from many of Trump's bad decisions.