Several months ago, I was talking with io9 reporter Alasdair Wilkins about how the hell this perennially unhip, unheralded, and mostly forgotten show stayed on the air for ten years (this is a mystery that's intrigued me for a while).
Alasdair had a terrifically plausible theory. In real life, Tom Welling really is Superman, but instead of fighting for justice, he coerces Smallville's cast and crew to make the show under the threat of death, sort of like Superboy-Prime mixed with that psychic kid from The Twilight Zone who exiled his enemies to the cornfield.
Alasdair and I never figured out why Smallville would be cancelled if Superman was holding the staff hostage, but after watching "Finale," I think I understand. Smallville was no simple TV show. It was a decade-long case study in delayed gratification, a tenth-of-a-century long con.