Before X Files, most hour long dramas shows were just episodic, with a basic relationship between characters. If you wanted a long, multi-episode story arc, you wanted daily afternoon soap operas. Then in the 80s, they started doing shows like Dallas and Knot's Landing, which were essentially soap operas, but with a weekly schedule instead of daily.

So people started liking the idea of a running story arc accompanying their episodic shows. The problem with X Files is that they didn't realize this until they were too deep into it to fix it. The episodic shows were great, but the subplot with smoking man, all those guys meeting in the dark, the black goo, etc, all turned out to be just mindless, aimless meandering, with no concept of a cohesive story.

People thought they were caught up in this complex world that had been built, and it all turned out to be literally nothing. Very disappointing. I was so pissed about it, that stopped watching the show at that point.