Your post just made me look this up and realize there were pretty large Indian (as in Hindi) populations in Guyana, as well as in neighbouring Suriname and Trinidad-and-Tobago. Who knew. Fascinating.
Yep, the descendants of indentured servants brought over by the British.
Same reason there are Indians in Fiji.
Where I live in New York, there are whole enclaves of Indo-Guyanese. If you see an Indian person, it's more likely they're from Guyana or Trinidad than from India.
I'm told there are a lot of Afro-Guyanese too but they just blend in to the local Black population.