I don't think sales were ever staling out. I still see this game on the top sellers chart on the Steam Indie charts all the time.I'm not a Patreon (I did however buy the game on Steam), but I'd be really hard pressed to be believe that at some point back those on Patreon essentially voted "more Grumps and less sex content". Much less that said patronage consists of anything more then a very very small minority who would actually prefer any real development time/investment being made on gay content.
I'd more guess that direction was strictly driven from the dev side in the hopes that attempting to present a more PC front in the current social climate would result in more overall sales for a game that had already started to stale out. Maybe it did. But I wouldn't bet on that net positive gain being all that big since again...this was game was never really set up well for that to begin with.
The Grumps were added to the game because of a contest that the devs ran. They were fans of the game, and officially entered, and obviously won due to their fanbase voting for them. The female winner was also a YouTuber, but just not as big, and more adult-oriented and more of a good fit for the game. I also see gay content asked for a lot, and I have been a Patron for a long time. They put polls out and the guys get a lot of votes for direction of new content, though not as much as the females admittedly.
Even if you are right though, I don't see an issue with it. I'm not here for the Grumps or gay content either, but I know there is more content coming that I DO want down the line, so if putting a couple of goofballs in the game and allowing the player to suck a few dicks allows the company to continue doing what they do, then what's the issue? I don't really understand the mindset that the entire product is ruined for you because there's optional content available in it that you don't like.