Musk has made it difficult for his banks to sell the debt needed to complete the deal. They are going to hold all $13 billion of it. It's a next-level move that threatens to bring a halt to leveraged buyouts.
A bank usually sells the debt used to create a deal. They can't hold anyone else's beer since they're holding Musk's. Or, as The WSJ puts it, "The Twitter move threatens to bring the faltering leveraged-buyout pipeline to a standstill by tying up capital that Wall Street couldotherwise use to back new deals."
Musk's debt is held because the appetite for it has decreased due to the financial condition of the Fed. Part of it is Musk's unpredictable approach.
Mr. Musk and Twitter have until Oct. 28 to close his planned purchase, and there is still no guarantee the unpredictable billionaire will follow through or some other trouble won’t arise. (If the deal doesn’t close by that time, the two parties will go to court in November.) That means the banks wouldn’t have enough time to market the debt to third-party investors, a process that normally takes weeks, even if they wanted to sell it now.
The emphasis is mine. Money types do not like surprises.