Charmless Mark developed a chip on his shoulder because so many of the other boys were much richer than him. He always wanted to be a tycoon.
His background might have given him something of a chip on his shoulder; he was a Sephardi, an Israeli descended from Jews who came from Arab lands, rather than an Ashkenazi, the elite of Israel .
He had a bit of a chip on his shoulder because he felt that other people who were not so good but who had the right background and connections had gotten ahead of him.