Earlier quoted context omitted.
>However, they're even not competing for the same audience. I don't think that's exactly accurate. Presumably the major audience for both types of streamers is young boys/men.
You have broadened the category widely enough to include both audiences. Given that guys typically watch gaming streams and undressed females for different reasons, I think there's finer distinctions in terms of which the audiences don't overlap.
When talking about aggregate, the small delta counts. This swings those uncommitted to looking for sexual content as well as attracting those purely looking for sexual content. To be fair, there are more hardcore sexual content out there that is just as free, so why would the population just looking for soft porn go to Twitch to do it?
It sounds more to me like they are competing more than just having different audiences.
EDIT: and more importantly, these sexual streamer are taking advantage of it, while avoiding other sites devoted to sexual content where competition would be harder for them.