Even without conspiracy theories regarding secret cabals that rule the world from the shadows, there is overwhelming inertia baked into the system itself.
A fairly recent study that I very vaguely recall pointed to this fact: the conclusion being that it is extraordinarily difficult to effect change within systems that are essentially self-perpetuating.
They're both creative individuals that are willing to buck the trend and change things in the way they think is right rather than toeing the party line.
http://fivethirtyeight.com/features/stop-comparing-donald-tr...
Notably #6 in the article.
But although he tends to vote the same as many other Democrats, he is very dangerous to moneyed interests in politics. No one's bothered to fix that for a long time.
Which is exactly why he can't win: those moneyed interests have...money.
Citizens United eviscerated of at least the appearance of a democracy.