This data seems to really support the hypothesis that the evolutionary origins of BDSM have something to do with encouraging sex between individuals of varying social status
According to most traditional models of pre-agricultural societies, men tended to focus on resource accumulation while women tended to focus on optimizing their Darwinian fitness via mating with high-status males. (This phenomenon still somewhat applies today.)
If BDSM encourages women to mate with males normally above their status, then it should theoretically increase their Darwinian fitness. This would also explain why many (but not all) women are submissive-leaning and many (but not all) men are dominant-leaning
If women are more likely to reproduce with a man who's into BDSM (dominant, powerful, etc.) wouldn't we expect to see more men being into BDSM? What sort of true-signalling is going on with BDSM?
Perhaps because, at least in the theoretical case, the submissive women are of nominally lower status/attractiveness/Darwinian fitness than our dominant man. This does somewhat violate the "impregnate as many women as possible" male optimal mating strategy theory though