If I were a conspiracy theorist, I’d say it’s because Tesla wants to be present in the Chinese market and angering Chinese state-associated media may be an issue here. But the more benign answer is that twitter has no video hosting and this must allow video links to YouTube, TikTok and other video hosting sites.
But not surprising. Tesla does have TikTok integration in the cars. I suspect Elon is a fan of it and doesn’t see it as a real threat. People are just not going to move from Twitter to TikTok.
The linktr.ee ban isn't a great idea, many artists use it to promote themselves on various non-SM platforms.