According to Matt Levine, that's "not how any of this works". The $1B is if he could not secure financing, but it appears we are now past that point. The relevant question is whether the Twitter board wants to sue in court to compel a sale.

Given what Musk does to the personal lives of his opponents, I'm not sure I would want to fight him. But given how many laws and rules he's broken at the point, I think there is a clear failure of justice if he can just do whatever he feels like without repercussions due to his common popularity.