Bighead's Character Change
I'm totally overthinking this, but for me it's fun to analyze shit that doesn't need to be.
Bighead's character seems to change pretty rapidly after he's pushed out from Pied Piper and hired to Hooli. In the pilot, he's portrayed as inept, but not dumb, and even seems relatively emotionally intelligent (at least compared to his later scenes).
I'd like to think that the scene where he hears the guys shitting on him might've actually been somewhat earth-shattering to his psyche. And from then on, he turned into the dumb asshole that remained for the rest of the show. After realizing how useless he was to the people he knew for years, especially spoken out loud, his ego shifted completely.
Of course this is all really just based on his much more tame characterization in the pilot. He just sort of seemed like a normal mediocre dude who fell into the tech world on complete accident.