I mean, not including embassy staff, what would Americans be doing in Haiti? These aren't "tourists" because if a cruise ship was stranded there, we'd be hearing about it. And it's pretty much a shithole country (as someone else famously said), so no one goes there for the lovely resorts and ambiance. So who? Are these American citizens just on paper like the Afghan "Americans" most of whom had never stepped foot on American soil? But somehow finagled an American passport?
While I don't know anything about these people that you reference, it is probably safe to assume that most if not all are Americans of Haitian descent who were visiting relatives.
There are probably a number of US NGOs there, and Haiti seemed to be a popular destination for church missions. I'd think that they should have left before now, but do-gooders sometimes lack judgement. Google "church missions to Haiti".
Yes, they are people who are there doing charity work. It would interesting to know why Haiti is such a mess. Could it be that it became independent before many of the other islands in the region? When it got its independence, it was the richest island in the Caribbean. Since then it’s been all down hill.
The Haiti indemnity controversy involves an 1825 agreement between Haiti and France that included France demanding an indemnity of 150 million francs to be paid by Haiti in claims over property – including Haitian slaves – that was lost through the Haitian Revolution in return for diplomatic recognition, with the debt removing $21 billion from the Haitian economy. https://en.wikipedia.org/wiki/Haiti_Independence_Debt See also https://en.wikipedia.org/wiki/Haiti_Independence_Debt#United_States_occupation_of_Haiti The US also helped keep Haiti impoverished.
I'm not sure what it is you find remarkable. Americans live all over the world. Especially in countries where we have some sort of interest. We have an Embassy in Haiti. Cruise ships travel regularly to Haiti. I think they've suspended them for now because of the violence. But the U.S. has plenty of business interests in Haiti. Many American companies have offices and/or production plants there: Pepsico, Coca Cola, Rent-a-cars, hotels, ...