My guess is that he took a meme for normal people ("that would make a good band name") and twisted it into a more nerdy version ("that would make a good domain name").

That makes sense. I assumed posting on hackernews implies the nerdiness.

Lots of nerds go to regular colleges so perhaps he’s saying he’s extra nerdy. (Though I think at this point we’re overanalyzing, the worst thing you can do to any joke.)

Yeah but if you keep analyzing it hard enough, the funniness underflows and then it's maximum funny.

Science, technology, engineering, and mathematics (STEM)

Yes, that part I knew.

Science is the systematic study of the structure and behavior of the physical and natural world through observation, experimentation, and the testing of theories against the evidence obtained.

Okay, but why?

Probably: "band names" -> Science, Engineering, TECHNOLOGY, Math college -> "domain names"

Learned about more things tech, started thinking about domains more than bands.