Trademark infringement, as opposed to copyright infringement, is all about customer confusion. If my vacuum repair shop is called 𝕏, then it's not likely to cause customer confusion if a sandwich shop opens up and brands themselves as 𝕏.
This may be why there are so many different X trademarks, and why none of them "went after" each other.
If I remember correctly, Meta's does pertain to social media, but as far as I know they're not using it, so it might get messy there.
Also, in case it's not clear. The 𝕏 is just a normal unicode character. Dude couldn't even be bothered to pay someone to make a logo for him.