Haiti vs Dominican republic

Many people do not realise this, but Haiti is not an island state. It shares Hispaniola with the Dominican Republic.

I find this interesting, as it allows you to do a reasonable comparison of how different policies, quality of governance etc have gone in each country. It’s a bit like North vs South Korea, or East Germany vs West Germany.

So here are the basic states for Haiti first, and the Dominican Republic second:

Independence: 1804 vs 1865
From: France vs Spain (was briefly ruled by Haiti also from 1821 to 1844)
Area: 27,750 sq km vs 48,400 sq km
Population: 10.0 mil vs 10.1 mil
GDP PPP per capita: US$1,317 vs US$8,672

So the Dominican Republic (once a colony of Haiti) has wealth per capita a massive seven times greater than Haiti.

Why do people think this is the case?