Can't really let you say that. Not only is SS far from being one of the first adult game on Patreon but starting early has nothing to do with popularity. Or else Akabur would have skyrocketed to the first place since he started his Patreon two years before SS (and me too, but that's another problem).
Anyway, I won't discuss graphical look cause I have trouble finding something appealing in SS, BUT, if you're interested in the reason of its success, I'd like to throw something no one mentionned I believe: SS is a vanilla game. Having a vanilla game helps A LOT in gathering a big community since you can basically catter to everyone. On the contrary, the more niche you become and the harder it'll be to get a big community.
And it creates a funny paradox: Since it's "easier" to get more patrons with vanilla games, there are more vanilla games than hardcore ones. Making said hardcore games even more scarce than they were in the first place since no one wants to take that road (in case the devs could enjoy doing it. Of course there is a part of game makers that are simply not interested in making hardcore stuff, but I'm not gullible enough to think that all devs take the path they chose out of passion only :x)