P.B. at The Economist site considers why Baby Doc Duvalier might have come back. It's all guesswork right now. But I think this point is very important:
Three-fifths of Haiti’s population is under 30; most of the country has no direct memory of the dictatorship. And some older Haitians express nostalgia for a time they remember as more stable, orderly, and prosperous. Lane pase toujou pi bon, says the Haitian proverb: Last year was always better.
Given the natural tendency of people to become nostalgic, even for the worst leaders (think of Stalin nostalgia among old Russians) and that young people in Haiti have known no functional government, one can see how Duvalier might gain support.
Also, 60% of Haiti's population is under 30? Yikes!