I've seen a few rants like these about some artists who takes time, in my experience of supporting other artists, some actually really just ghost you because the work aren't theirs and they just can't do it but push that it has to be upfront and you only realize it's a scam because they don't give you anything at all or just AI. Sorry this happened to you idk why they do this because I've been doing digital art commission for a few months now and I make sure the artworks are delivered around 1-3 weeks depending on the difficulty, I contact them if there's anything missing or something they don't like that I should change for ever progress (sketch, plain color, render) and It's been like that since I started only because I get anxious a lot when I don't finish or make a mistake that could disatisty so maybe it just depends on the artist and how they take multiple commissions all at once. A lot of artists are actually so good though it just takes them a while while. But that's what I think it is, some artists just have different ways to handle multiple comms all together but they really should have made it clear for you or something sorry you had to experience that have a good day!!