He could have put it into developing and deploying renewable energy development and deployment. So, no, that argument doesn't work.

It is possible he thinks he can use Twitter to drive politics, and maybe government spending, in directions he favors.

You're right about politics. The SpaceX Mars mission is ultimately tied up in NASA funding/approvals. Twitter is the hangout spot for the journalist profession. So even a slight manipulation of the algorithm could result in incalculable benefits to the Mars mission.

On the other hand, it's possible Musk is just getting revenge for Twitter censoring his friends at the Babylon Bee...