Or, hear me out, it might just be hobby. Plenty of people create games just for hobby, even if it's AVN. Similarly plenty of people write stories, create music etc... as a hobby, even lewd stuff. Why you might ask, well that's because it's a way for them to express their creative side. Sure, most of them would be extremely pleased if they happened to hit it big and could make living from their hobby, but the reason they started it originally was as a hobby. Very few devs actually make enough to make a living or enough money to just justify their motivation for creating games like these. Biggest reason why they have patreon etc... accounts is to recupe the costs for making that game, since game development, even as a hobby costs money. That's also why so many devs end up abandoning games when there's problems like this dev had with Patreon, since it sucks the joy of making the game having to deal with it. Or abandon their game because constant negative bitching, not constructive criticism, sucks the motivation in working on something time consuming for people to play.
Now sure, there are some cases where person thought that it would be easy quick cash in, but those cases actually end up usually producing subpar shite that gets abandoned pretty fast, unless they manage to garner following to fund them. Considering this game lasted as long as it did, i'd say that the dev was not in it for the quick cash, but honestly because they wanted to make the game, but then outside factors killed the joy of making it.