I wonder if it has something to do with stress and being highly involved in a subject.

Let's say I get involved in a pet project, put lots of bloody time on it, and get involved on it mentally. I can become a jerk when someone criticize it.

Taking critics is good. But it is very hard when you put lots of effort. Steve Jobs did put lots of work into Apple. That could made some of his reactions a backfire that people perceived badly.