I recognize the name because the island had a weird role in an odd novel I read (The High Mountains of Portugal by Yann Martel - save yourself the trouble and don't read it, it's just plain odd.)

From your article (it took a couple of tries to fix the link, but I'd seen this myself this week so figured out where it was):

While other Portuguese sugar mills relied on enslaved people solely for manual labor, in the São Tomé sugar plantation system, enslaved people — largely from what are now Benin, the Republic of the Congo, Angola and the Democratic Republic of the Congo — performed nearly all the tasks, from the harvesting and processing of sugarcane to the carpentry and stone masonry needed to build and run the mills.

This made São Tomé "the first plantation economy in the tropics based on sugar monoculture and slave labour, a model exported to the New World where it developed and expanded," the researchers wrote in a new study, published Monday (Aug. 14) in the journal Antiquity.

"The island's plantations were so successful that in the 1530s, São Tomé surpassed Madeira — an Atlantic archipelago that the Portuguese used for their lucrative sugar operations — in supplying the European markets with sugar, and dozens of sugar mills were built." - unpaid labor will do that.