Modern day Haiti is largely a Catholic country. This was news to me when I read it in high school because 90% of my family attended Protestant Churches.
Plantation system in Haiti was possibly the WORST in terms of brutality.
The African belief systems are what gave the enslaved people the spirit to set off and continue the 13 year revolution against blan(whites) and THEIR god. Their god who, according to blan,,,cosigned them enslaving other human beings.
The mixed race & free children of the French, who also rebelled(for different reasons), were largely Catholic, so the Catholic institutions remained in the country post-independence.
The Africans who were forced to practice Catholicism while enslaved, secretly worshipped their own gods by replacing/hiding them in the form of Catholic saints. I beleive they continued this tradition/culture after 1804.
Protestant missionaries have been to the island converting Catholics and those practicing Vodou for decades. Catholic and Protestant churches had money, schools,jobs, & institutions that connected Haitians to the larger world.They provided access to resources in a country that doesn't provide those resources to her people. That is, to me, the reason why majority of Haitians became Christians over the centuries. I also believe that some reached the conclusion that the French were practicing a corrupted version of Christianity, and that they are practicing a truer version and living according to the tenets of the faith.