I dunno, is it that baffling? It seems like he really loved using the product but didn't like the leadership, and he just wanted to own it so he could mess around and have fun following his own whims.
Once you get the idea that he doesn't actually care about financial success it all seems pretty reasonable. Like any hobby, for X/Twitter to be a "success" it just has to amuse him, and based on his usage of the platform it seems to be doing that.
The amounts of money he's losing are staggering to us but also meaningless to him. Our society has allowed him to accumulate so much wealth that nothing he could do "wrong" in a business sense would meaningfully impact his lifestyle.