@neil

Because he's trying to recapture his youth.

"X.com was an online bank co-founded by Elon Musk, Harris Fricker, Christopher Payne, and Ed Ho in 1999 in Palo Alto, California. In 2000, X.com merged with competitor Confinity Inc., a software company also based in Palo Alto. Elon Musk was attracted to Confinity because of its easy payment system. The merged company changed its name to PayPal"

https://en.wikipedia.org/wiki/X.com