Both the most vulgar and selfish interest, and the most principled passions, seems to play a role in history at different times. The most important contributing factor, though, is selfish interest of large groups of people, because the sun of it's many little influences do not cancel out, unlike the actions of principled actors. In exceptional times, good intends are allowed to take the front seat just as long as necessary, by the many behind the scene who will silently weight toward the prompt reestablishment of "business as usual".