I assume they have more going on than being an outright scammer. Most likely, these are caused by depression or outside forces. THIS much time and effort put into a project just for it to be cast aside means there is something more happening.
I only hope that the creator will come out and talk about it.
IMO he over-promised and realized he couldn't deliver. After so many failures to deliver some people do just give up and ghost, hope it goes away. That is easier than owning up to the fact you were unable to follow through for whatever reason.
Literally the last update he posted was just a hype update about how awesome the regular updates were gonna be and all the other jazz. He had already done hype cycle of another game right before his updates to this one stalled for almost a year.
Just seems like the most obvious reason. He went missing before any conflicts, his updates stopped a long long time ago. Sure i hope he is alive and well, but the most sensible reason is that he didn't have to work.
He said a full time salary was 200 a month where he is from. He had made literal year to years of income every month off this game. And even today he is doing well if that is the case.
People need to stop with the delusion and justification for someone who has a history of not following through, and just look at their past behavior for what is.