Paid for (at least partially) by the U.S. government [1]. You can't easily say "no" to your own government even if you are a foreign asset.
[1] https://www.independent.co.uk/tech/spacex-ukraine-elon-musk-...
The Saudis are major shareholders in Twitter, although personally I doubt they're telling Musk what to do so much as being content to let him run it into the ground; it's a win for them whether Twitter under Musk succeeds or fails.