Recalling back in 1996 or 1997 when one of my co-workers was approached by some dude wanting to create an internet banking site and call it 'X'. You see my friend had been around the internet a long time and had registered X.com back in the early days (there are only 26 single-letter .com domains) and this dude wanted it - real bad. He offered a lot of money. My friend was savvy - "I don't need/want your money, but how about you exchange it for some equity in your company?"
Anyway turns out "this dude" was Elon Musk and if I recall correctly, X morphed into PayPal.
I note the continued fascination with the letter X.
No telling who holds X.com these days. The site responds, but there's no content and the current holder apparently doesn't wish to be made public. My guess is that Elon or one of his companies still has it and doesn't know what to do with it. If any normal person acquired it post y2k when all of the dictionary words had been exhausted (FWIW I grabbed the second to the last of these), they'd have paid an enormous amount of money and would've wanted to capitalise on their investment.