Well, there’s a few reasons.
The main reason Haiti is poor because Haiti is the Capital of African Diasporic Struggle, and therefore will not be allowed to form a sovereign government, develop independently, or be revived as the symbol of Black World Resistance that it is. Haiti shook the System of Global White Domination to its core and sparked a continent spanning Black resistance struggle that is still active today; albeit relatively small, fractured, and isolated.
Haiti is poor cuz White people fear Haiti and have not forgotten Haiti’s potential and power! That’s why Haiti is not only held in poverty and political turmoil by the Western Powers, but why they want the Black world to always be reminded that Haiti is the “Poorest Nation in Western Hemisphere.” It’s military and economic war against Haitians and a psychological assault on the African Diaspora.
Beyond that, Haiti is poor for the same reasons that Jamaica, Trinidad, Panama, Honduras, etc are poor; because of Capitalism and Imperialist exploitation by the Colonial Powers.