Amazon added epub support to Kindles a while back, and deprecated mobi. It still has some issues with epub formatting though, I've had to tweak some files using a Calibre plugin to make them render properly on the kindle.
I think it is kinda newsworthy because Elon already threw his toys out of the pram when Threads launched and started eating what was left of Twitter's lunch. That this one guy just reposting the already public data about his jet's movements bothers him so much is delightful.
If they can afford the power bill for all of that A/C maybe.