This is an interesting question and probably deserves an entire book devoted to it.
I would suggest two reasons for the amount of research on Jamaican creole.
Firstly, it is the most populous of all the English-speaking islands in the Caribbean and so there is a lot of evidence.
Secondly, although the UK has many residents who trace their ancestry back to all of the islands, the vast majority are descended from those of Jamaican origin. Because of this Jamaican creole can still be heard on the streets of London - which has given it greater prominence and prompted more research.
These two factors have also led to Jamaica having a dominant influence on Caribbean culture.
Hope you fidn this helpful!