They don't need to advertise anywhere.
They're going to twitter for a reason.
“X’s owner now has the ear of the president-elect, a man who has a long history of helping his friends, and punishing his enemies,” said Max Willens, senior analyst, at Emarketer
But Twitter has been bleeding users. And since the election there has been a very public exodus by bigger names. So this isn’t about “go where the viewers are.” This is “spend money to stay on the good side of someone who might be even more inordinately powerful with an incredibly powerful and vengeful sidekick.”