I doubt that he will be forced to go thru with the deal but ultimately he will have to pay for not going thru with it. That's why they have a clause in that speaks to what happens in case someone backs out. Right now the dollar amount is 1 billion dollars but I suspect that Twitter has reason to take him to court for a greater amount. He's totally disrupted Twitter's business for no reason related to Twitter. He'll have to pay big for that.
If I read the agreement correctly (and if Matt Levine has read it correctly too :) ), you cannot just walk away and pay the $1B. There were specific reasons tied to walking way and the primary one was not being able to secure the funds. That is not true in this case. There were commitment letters from the banks.
