Trademark is established by use. Registration can offer an extra level of protection, but is not necessary to own a trademark. Elon has been using his X.com since he bought it back from PayPal in 2017, which interestingly is around the time some of these other 'X' registrations took place.

Is Meta using the trademark "X" for social media though? I haven't seen it. They're not gonna win anything if they're not actually using it. That's like the first and most important thing.

and it sounds like the logo is just a unicode character <https://www.compart.com/en/unicode/U+1D54F>, or from a standard font <https://catalog.monotype.com/font/monotype/special-alphabets...>.