How did leftism become ociated with intellectualism?

It seems that academians and intellectuals have always gravitated towards leftism. Why? I have heard several explanations including the socialist movement of Herbert Marcuse starting in Columbia University, the "noblese oblige" of the aristocrats (Diego) Rivera & Trotsky; and the struggle for power by names such as Castro & Che; and finally the somewhat "collective culture" of the Jewsh people in general which tend to gravitate towards positions of power and wealth. If these are not correct, what else can it be?