Yes they do, it's called specific performance. It's not the usual remedy for breach of contract, but in certain cases the court will grant it. I believe M&A agreements are one category of cases where US courts are inclined to grant specific performance, but I'm no expert.

Why wouldn't courts have the power to do that? If the court rules you have no grounds to terminate the contract then you will have to execute the contract as originally agreed upon.

Can they force all the banks that agreed to loan them money to go through with it?

How Musk gets the money in order to fulfill a contract he's entered into is immaterial unless he goes completely insolvent and still can't fulfill it, which will not be the case.

They can force Musk to sell his other assets to complete the deal.

As long as Musk has ~40 billion of Tesla stock and can get ~20 billion additional dollars in cash (can get, not just has already), yes.

They can force his banks to sell enough Tsla shares to buy it

The banks also signed contracts stating they’d loan the money using Tesla shares and Twitter equity as collateral. They can’t get out of that contract just because musk wants them too.

Well the court could obligate Musk to pay damages. One (simplistic) possibility might be to take the value Musk agreed to pay minus the current value of Twitter and force Musk to pay that. Then in theory Twitter would have received same value in the end.