If the show hadn’t been as successful as it is (and I’ll readily admit that I was skeptical, as I had been each time someone tried to adapt it into something over the years) the end serves as a finale that doesn’t really feel unsatisfying as far as single season shows are concerned. In addition, if those watching the show were even remotely interested in checking out the source material, the point where it would essentially be leaving off is a perfect way to transition into reading the comic in order to get the remainder of the story.

But, it is a success and while your point made that investing in a number of the characters that (at least presumably) got wiped out in the gas explosion is valid, many of those characters are mere drops in the bucket compared to the characters they could bring in to replace them.