> How much of this is the result of parents allowing children to play games unattended with games they themselves have not played to vet?
None of it. You can try it. You can have a million parents leave a million children alone for most of the day, and not even a bitmap image of one cartoon coin or anything will magically be created, much less the code and distribution channels for a whole game. It doesn't make existing "wholesome" games automatically devolve into other games either, the code and assets don't change at all.
The people who actually do make these things, who do exploit some parents having a lot on their plate: where were their parents then, and where are their peers now? The crime of "not paying enough attention to what your child is doing, which results in a person you love being harmed, and you paying money", is tiny versus the crime of "ruthlessly preying on children for financial gain". Looking away when your child plays such a game is nothing compared to looking away when people make and distribute them.
I don't have children so I'm hesitant to point fingers at parents. I have the ability to make derpy things to sell to children, and I'm not doing that also because in my mind, only a.) children and b.) very careful, well trained and aware adults should make entertainment for children. So unlike parents, I judge those "creators" mercilessly. I cannot even stand the overly "hyped" streamers and youtubers who makes sure they don't swear to be "family-friendly" and not get "demonetized", but otherwise talk crap 24/365 that is fit to turn any brain to mush... but apps and games pushed onto kids directly is yet another level of depraved.
Where is society making an effort to warn parents, that you get to call them lazy for maybe not even considering some people would be so sick and morally bankrupt? What effort was made since Elsagate to warn anything about that stuff? That there's millions of dollars on the line has nothing to do with it, just lazy parents?
Lazy, deplorable society, is what I'd call it.