It goes back a bit further than that.
If the series does not have comedy in it, a bad end is all but assured. Drama leads to tragedy. U.S popculture tends toward Drama>will to survive RISING>bullshit powerup overcoming fate>good end.
For an example of this occuring, you need only look no farther than Higurashi season 2. Season 1 was all, 'fuck, humanity is doomed we are so flawed BLARGH I'm dying' and season 2 basically became a 'now we got hope and are fighting against fate- YAY SCOOBY FUCKING DOO'