Several well-known people in tech are notorious jerks. So I don't think being kind is a necessary condition for career success (though it can't hurt). But I suspect it's necessary to have a happy life.
Being well-known also means your worst moments get more attention than might be deserved. Even kind people have bad days, but a bad day for a Fortune 10 CEO can follow them for life. Maybe unfair, but it's one of the (more reasonable) reasons for the inflated paycheck.
Many of such said 'jerks' are often the ones at the top, however: i.e. nobody above them to be put off their ability to communicate or display typical good teamwork.
