So Zuck practices/practiced BJJ. I have a brown belt in BJJ and with experience coaching competitors and classes, so I feel qualified to analyze white belts. You can see some competition footage of him as well as a roll with Lex Friedman who, say what you will about him, is a BJJ black belt[1][2]. In his no gi competition he gets some real resistance even in the stand up right at the very beginning. Then you see him defend submission attempts and, though sloppy, he manages to figure out how to pass the guard. If you combine that with his footage with Lex Friedman, you can see him doing honest to god BJJ. This is significant because there are celebrities who will train BJJ who don't get "real" looking BJJ - which is to say that it looks as if their practice does not include resistance[3]. Distilling its history as distinct from Judo, BJJ, the collection of martial techniques, prides itself on the effectiveness of its techniques against resisting opponents, so "unreal" BJJ is the subject of ire. Celebrities will often times get private lessons (with prestigious coaches) so they don't risk getting injured by the general public and putting some movie shoot, and all the employees working on it, on delay. So it's cool when Lex Friedman puts Zuck in real dilemmas and you see Zuck think through it with techniques that make you go .

Musk, on the other hand, name drops a bunch of different martial arts he tried as a child[4]. It arouses my ire even before you give them the 9999 billionaire hate-coefficient. It's like your uncle who used to bench 4 plates. It's the kind of thing I grin and walk away from IRL. This man would have pointed to his competition experience if he had any. He is 51 years old and wears it. Not like it's a problem until he's walking around telling people you'd beat a practicing martial artist in martial arts. Steven Hawking's oil paintings wouldn't be subject to harsh critique unless he goes around bashing the cis teens who painted the chapel.

To round it all out: Zuck wouldn't have had to take an asprin after taking off balance and climbing on top of him on the floor. There's always a market for "the striker vs the grappler" fights. But in those kinds of fights the data bares out that the grappler has the edge. In the UFC, the most prestigious league, a base of wrestling makes more champions than any other base (they, however, must be great in every dimension to be the best anymore). So even given Musk has an equivalent amount of experience in kyokushin, the most MMA relevant art he listed, and comparable athleticism then he's still at a disadvantage. But in every way he's not a real rival for Zuck's white belt BJJ. It's smoke and mirrors. Zuck might as well bring a dog collar into the ring and try and put it around Musk's neck. He should bring a book in case he gets bored fighting Musk.

[1] https://www.youtube.com/watch?v=qV6GC3p4jH0

[2] https://www.youtube.com/watch?v=1Wy-6z17up4

[3] https://www.youtube.com/watch?v=dFeaa8nIOgY

[4] https://www.youtube.com/watch?v=cPRah0RJTs8

Probably, I haven't perceived a transformer sober since '11