When you have ~$200B you can afford to lose $40B destroying on a social chat app, and a few $B in goodwill/consumer sentiment for your other holdings.
I’d be surprised if the hit to his net worth from the purchase as less than $80B
He gets to be in the public eye and news all the time. Gets to be defended by fanboys while making fun of disabled people and laughing at design people who work with Figma. He gets to delist anyone he dislikes. This role gives him power and attention on a global scale.
Seems like a great investment of $80B if that floats his boat, which it seems to.