Very often it is the case that such a project is started by someone who had quite some time to spare. This entire field is too vague and even if you have the best of intentions, start a company, do all the legal work, buy hardware, start developing, render graphics and all of that, even then there is only a small chance that it will be a financial success. The likelihood of developing a failure is very high.
There are only a few devs with a real financial success from a business point of view. "WildLife" is one of them that are run like a real business with an office, employees and so on. Milfy City is the result from a single person, who hit the jackpot by coming into the market early and now only milks it. This is not how a real business is run.
You can see this with a lot of these games, when you look at their patreon pages. Years of work for a pretty good game with a nice story and all they have are 200 patrons pledging an average of $10 each. This pays for some bills and big rims for the car... but that's not the basis for a sustained business.
