I think they didn't know where to go with it, so they just kept making it more crazy and plot-twisty; to the point that it actually became kind of boring because almost every week there was some plot "swerve" and it became pretty cliche. By the end I got to where I didn't even care anymore.
It reminded me of the Resident Evil movies, where each movie they made things "bigger" to by the third movie the whole planet was almost dead and it was like "ok why do I care anymore", and they had nowhere else to go.