The $44B Twitter/X buyout was not a failure. For example Fidelity has its $19M investment in the buyout - now xAI common shares - marked at $62M (up over 3X) as of 12/31/25. It was certainly valued even higher on 1/31/26 after xAI had an oversubcribed fund raise in January. All before this merger announcement.
The fact that it had to be successively bailed out by xAI (which itself was funded by Tesla) and now SpaceX shareholders is exactly what makes the acquisition a failure.
He spent other people's money (or maybe even imaginary money) he couldn't have used for himself (since selling off major stakes in your company is a big nono)