Compared to the $44B he owes them, finding some way to trigger the special clause that only requires him to pay $1B may be great.

AFAIK the $1 billion is just the "I don't want to do this anymore" clause he signed - if he just pulls out, the same applicable to Twitter if they pull out.

The weirder part is technically Twitter can sue to force the deal to close anyway.

No it's not. It's the "you started this, if you can't pull through on your financing you still have to pay us something for all the turmoil" clause. Musk has already agreed to buy Twitter: only extreme circumstances could lead to him not having to pay the amount he agreed to ($44B).

I don't think we're disagreeing? Musk doesn't have the money cash in hand, so the default position is "he doesn't have financing". The most he can become personally liable for I believe is the $1 billion fee.

No, he is liable for the $44B offer he made and signed a contract for. Now, if say Tesla and SpaceX were to go bankrupt tomorrow and he would lose access to these funds, the $1B clause would activate.

Remember that he has already secured the funding, he has filed information about that with the SEC, and he has already signed the contract for paying Twitter's shareholders $44B in exchange for sole ownership of the company. Neither of the parties can pull out now: the deal is done. Only extraordinary circumstances can undo it anymore.