it is now clear that the answer is trump's presence in the epstein files, although it's not clear what the lingering concern about it is. he's already been convicted for soliciting a porn star, and he seems to have benefited from it, but he can't run for office again.
musk probably learned this from non-government sources. he probably doesn't have a mole in the fbi, he probably just knows people that know people that know that trump was there.
but, now that it's out, musk probably has no further leverage over trump and this sad and twisted situation, which we haven't seen in the united states since the 19th century (when rockefellers and carnegies had immense power behind the scenes), is now over.
what trump is focusing on is trying to help the republicans win the 2026 election for california governor, and framing it as a choice between law and colloquial anarchy is the best chance he's got. it worked in the upper midwest after the shooting of george floyd.
if the republicans can swing california, they won't need to rely on dwindling support in other regions.