Normally I do figure that the dev decides to blow off the game due to greed and a lack of ethics. That is based on 100s of abandoned games on here. However, we know the update was very close to completion so it makes more sense to release the update and then ghost everyone in order to string out monetization for a much longer period. Devs who are doing that also tend to post on Patreon every few months to make it seem like they are doing something. I know devs who keep the con going for years on end with that method.You don't have to imagine the worst, ghosting is pretty common just because you lost motivation to do something. Decency would be to inform your supporters when you take money, but it is what it is
But this game didn't have much support anyway. So ripping off supporters doesn't seem to be the prime factor in the disappearance.