Camelot - I didn't find it surprising that it was cancelled. IMO it got worse with each episode, plus it suffered from a lot of unfavourable (but IMO very fair) comparisons to Game of Thrones. Ratings weren't great, reviews weren't great.
The Event - the problem is it took so long before it "started to get good"!
It did improve after its forced re-tooling during the longer-than-normal mid-season hiatus, but it was way too late by then, as the damage had been done.