No budget, maybe. Or not enough materials for creating season 2?
The latter is a common misconception, they have plenty of content for another season
Well, its not too strange for animes to not have season 2
It's also strange to do an anime of the spin off. It's weird that they'd do an adaptation for that and not expect a second season of the main story, but the spin off didn't do good so we are in a weird place right now of speculation.
I don't think it was that strange, it was just another cash grab. They're trying to get as much money as they can from the series
I mean strange as in if they were invested enough to adapt the spin off, then they would most likely be interested in a sequel as well. I think, commercially, that it's hard to say a spinoff would make a lot of money when it depends on prior knowledge of the main series (which aired 2 years prior) so it'll be harder for people to get into it. I don't think Danmachi is that big to assume that a large number of general anime/manga readers keep up with Danmachi but I could be wrong.
But we could definitely talk ourselves into a circle about this topic XD