There's always an exception to the rule for any group of people. Perhaps Vorn was one of the few smart Gamorreans.
Have you read the middle of the pack X Wing Novels like Wraith Squadron, Iron FIst and Solo Command? In those books, there was an intelligent Gamorrean pilot named Voort SaBinring aka Piggy. He was highly skilled in mathemathics and navigation in addition to being a pilot. In the book X-Wing-Mercy Kill, he retires to become a mathematics professor.
https://starwars.fandom.com/wiki/Voort_saBinring