IG links are broken, here's the video, just type instagram in the url:
https://www.TYPEINSTAGRAMHERE.com/p/Cr8v1iVJUB_/
Here's the video and it is sped up, but he is also crossing the carpool line, cutting in and out.
I don't know the context, were the other cars being overly aggressive? Personally, the easiest thing for me to do when other cars are trying to race is wave and not engage. Let them "win" their race.
On a side note, if you have ever driven that section of the 5N in Socal, people are NOTORIOUSLY slow for such a wide freeway for no reason. I'm not talking about traffic and rush hour, but just people being in the passing lane pacing the other lanes, wide gaps between cars. I don't get it, it's maddening. It's no excuse for cutting in and out like that, but maybe he had to poo.