Conan Doyle was fascinating, I highly recommend the biography Teller of Tales, he was prescient about a lot of things (submarine warfare, other military issues during WWI) but also fooled by the rampant fraud in the spiritualist movement, like the Cottingley photographs.

This article makes it seem like he personally investigated the cases, he didn’t. What he did was help publicize them and write long book length summaries of the evidence to convince people. He also published a “pamphlet” on Belgian colonial exploitation of the Congo. He worked directly with the lawyers / investigators to get the facts and used his fame and writing ability to get public attention.