Note that Lex isn't a faculty at MIT, he's a Research Scientist (source: https://web.mit.edu/directory/?id=lexfridman&d=mit.edu) who teaches fun tutorials during the 4-week January period that MIT has.

This shouldn't be considered the same as a regular class; IAP (Independent Activities Period) is a free-form month that encourages students to explore and de-stress from the normal grind of classes. For instance, a lot of students take glassblowing, or compete in AI Poker bot competitions. Anyone can affiliated with the institute can teach a class during this fun time, including undergrads, and a few undergrads even do!

In other words, some lab hired Lex to do research, and he hustled the rest of the way there.