I mean, honestly... it makes sense. I'm in a vanilla relationship now, but in my more wild days it was always challenging to find a female to have a threesome with. So hard they call those girls "unicorns."
People want a safe place to find threesomes that doesn't being the element of sleaziness that CL brings.
OKC is legitimate and seen as less scuzzy than CL, and less bot-overrun than Adult Friend Finder.