The answer is not some mythical pact with Satan as Pat Robertson would have you believe- unless the Satanic force in question is the world power and financial system, which was just as corrupt in the nineteenth century as it is today.
The French colonial system was based on creating and maintaining harsh distinctions of class and race. Your position in the social order was based primarily on your percentage of white blood, so that Haitian people were turned against each other by a race-based class structure. The Haitian Revolution drove out the French and ended slavery, but it failed to abolish these class divisions. The vast majority of Haitian people went from being slaves before the Revolution to being serfs after it.
Even then, Haitian society may have been able to address this issue through a series of reforms over time, but Haiti was an international outcast after the Revolution. Without any ability to engage in trade with other nations, its economy was ruined. The only way the new leaders of Haiti were able to restore relations with the international community was by agreeing to “compensate” the former plantation owners. This boggles the mind, but instead of being held accountable for their crimes against humanity, the plantation owners had to be paid back for their losses on a massive scale, leaving Haiti in an economic shambles from which it never recovered.
So there you have it. Haiti never got the chance to make a fresh start because its revolution was incomplete. The external name of slavery was removed, but the internal reality of it largely continued, producing a society twisted by social divisions, injustice and lack of opportunity. The Haitian people are still suffering for it even today.