I really liked the first season, but can also understand the cancellation. I read some of the news articles, but none really provided an explanation or reversing a renewal 4 months later. It was a big cast, which I suspect had a lot to do with the cancellation. The big ensemble casts are problematic for scheduling. A friend of a friend worked on the Sopranos, and that person said the last few seasons were a nightmare to film because the actors were all so busy with other stuff.
I also think it was also a well done season that clicked, but seemed like it would be really hard to replicate for a second season. I wouldn't be surprised if HBO, the cast and crew reached the same conclusion.