This.Its not thier negative attitude that made them Successfull
Like @CainsControl says there are alot of unsuccessful people that are a$$holes, there are alot of successful people that are nice and friendly. There's a certain level of approachability you have to have to garner success. You can't be some miserable anti-social woe is me let's throw a pity party for me type sociopath and be successful. You have to put a face on for the public you have to deal with. You have to hide your true feelings and opinions about certain matters and issues to yourself. You kind of have to be an actor and lie to people just to get their nod of approval. Once you get what you want and can work on your own terms, and have success doing so, you can afford to be an a$$hole to be arrogant to take risks, cause you have little to lose and more to gain in those circumstances, depending on what they are, other than that negativity in general is something to be avoided if you want to be successful.
Also success builds confidence....so some cockiness might be seen as that.