I'm sure it almost always starts as a free time thing. The problem is that nowadays most people on Patreon asks at least 5€/$ a month at minimum for 1/2 updates a year. Put in perspective, that's the cost of two commercial games per year per sub.Intertwined's always been a free-time thing. Nyx plays it safe and doesn't stick to strictly framed development. When it's ready is what you get when questioned. So all those calculations don't work as a judgement I reckon. Take it (and pay) or leave it.
I believe that if more people would ask only for "a coffee a month" (1 - 1,5€$) the number of subscribers would be much higher and the complaining much lower. As for me, there're about a dozen VNs I follow, but currently I subbed only to 5. Sometimes I suspend a subscription if the author takes too long between updates, sometimes I give a "one time" heftier donation when a new chapter is out because I feel bad not paying for other people's work, but it gets tiring to micromanage all this Patreon stuff.