Why Heroes was cancelled

According to the latest news from Hollywood, the superhero series Heroes was cancelled for two reasons: a) low ratings (a good enough reason to pull the plug) and b) high costs. 

So...what happened?  How can the show which was on everyone's must-see list only four seasons ago was given the shaft?  How can the series be cut in mid-stride and leave forever unresolved the fates of such unforgettable charactesrs as the mutant cannibal Sylar, the self-righteous human spy Noah Bennett, the quirky time-traveller Hiro, and the conflicted clan of the Petrellis who was responsible for setting up the stage for the creation and proliferation of these super-powered outcasts?

Like the Manny Villar ads, it's too much of a good (or bad) thing.  The Heroes storyline got more lost than Lost (another show by its producers, btw) when it got obsessed with building and rebuilding the world and origins of these mutants to the point that the structure became a labyrinth which confused the readers with its twists and turns?

True, the storyline on a world gone bad after one mutant screwed up in the first season was disturbing - and compelling.  Who could forget the episode where angelic Peter finally became kick-ass and nuked it out with Sylar in a life-or-death battle?

But the producers kept milking that storyline for all its worth.  We kept going back to a dark future that's either incinerated by a nuclear holocaust, or devastated by a plague.  And it's always a world where mutants or people with powers are hunted down, killed, or thrown like cattle in concentration camps.

If I keep mentioning mutants, it's not accidental - there's a lot that Heroes has borrowed from X-Men including that alternative universe which always ends in mutants (ok, people with powers) being treated with the Final Solution. 

It became tiring.  And the producers were so focused on this grim tale that they forgot why Heroes clicked in the first place - it was the optimism of the show, the delightful discovery that a cheerleader or a simple male nurse can suddenly realize her immortality or his capability to adopt the abilties of others?  It was Mr. Joe-becoming-Superman that made Heroes a fun show to watch.  That was why it was called Heroes.

By third season, the optimism was gone - and the people with powers were just on the run for survival.  And the audience (like me) stopped tuning in.