Because having a bully-ish personality does make you a more efficient salesman (the less ethics you have, the more strategies you can use to convince people to

Because having a bully-ish personality does make you a more efficient salesman (the less ethics you have, the more strategies you can use to convince people to buy stuff), and it's easier to be a bully in tech-related jobs. Jobs where being an asshole can be an asset attract assholes. Simple as that.