Musk could use this to get Trump's tax returns. That could be blackmail material on Trump. (And the Supreme Court, in the same way.) He could leverage that into getting an even freer hand to do whatever he wants.
Now who's ruling the country? People talked about "President Musk", but that was just sarcasm (we think). But he could use this to really be "the power behind the throne", with money, media clout, and blackmail material on all the office holders.
Is that just tinfoil-hat level paranoia? Or is it what's really going on? (Or, between the two, is it not necessarily what's going on, but still a real concern?)