There's no question that Twin Peaks was a widely successful series during its original run, not only inspiring a legion of great shows but arguably spearheading the must-watch-TV movement in a pre-social media age. Despite that acclaim, the show isn't without its faults, as most of Season 2 is -- well, it stinks. Despite having some of the straight-up weirdest moments of the series, Season 2 just doesn't hold up against Season 1. David Lynch, co-mastermind of Twin Peaks, agrees with that much and he's not afraid to share his opinion on the matter.
Whoa, whoa, whoa! I don't think the people in the back heard that. What'd he say?
HE SAID IT SUCKED!
That quote comes from TV Line, who asked David Lynch if there was an aspect of the original series that he was most proud of. While Lynch was pretty happy with the pilot (you might think it's lame for the first episode to be the favorite, but the Twin Peaks pilot is seriously good), he, maybe unnecessarily, added that the second season sucked! Season 2 is certainly not without its bright spots -- it has some weird/great episodes -- it is not nearly as solid as Season 1. Season 1 surely had the benefit of being much shorter, but there are a number of reasons why Season 2 didn't live up to the unbelievable hype following the Season 1 finale cliffhanger.
For the record, David Lynch didn't have that much to do with Season 2. He was involved in some of the earlier episodes but then had to drop off due to directing a movie (some say he also left because his motivation wasn't in it anymore), only coming back to direct the last episode. So, that at least partly contributes to the season's scattered focus.
As for another reason why Season 2 isn't so hot, you can mostly attribute it to the show wrapping up its central murder mystery about half way through. America was obsessed with finding out Laura Palmer's killer, and when they did, there wasn't enough there to keep them coming back. They tried to introduce a new killer into the mix with ties to Agent Cooper's backstory, but it failed to fill the void in a meaningful way. Plus, it has some filler storylines that weren't very satisfying at all (looking at you, James!).