Dictators, unlike Democrats, depend on a small coterie to sustain their power. These backers, generally drawn from the military, the senior civil service, and family or clan members, have a synergistic relationship with their dictator. The dictator delivers opportunities for them to become rich, and they protect him from being overthrown.
To understand why dictators fall, it helps to recognise factors that produce a perfect anti-dictatorial storm. Barring missteps such as those that led to Gaddafi's undoing, a dictator's survival can be at risk because of newness in office, poor health, or old age combined with economic trouble.