I actually think it's probably pretty simple underneath the facade - Musk offered to buy Twitter for a lot of money. The market tanked and Musk doesn't want to pay that price any more. He thinks he can strong-arm Twitter and either not go through with the purchase or force them to accept a lower price. The law does not support this, but Musk has a history of being unbothered by the law and there are examples (not Musk) where this tactic has worked to reduce the purchase price by hundreds of millions of dollars.