Eu sinto que o segmento 'Declining Ratings' na página da Wikipédia de Twin Peaks resume muito bem as razões ( mas vou resumi-los ainda mais com os pontos abaixo).
With the resolution of Twin Peaks' main drawing point (Laura Palmer's murder) in the middle of the second season, and with subsequent story lines becoming more obscure and drawn out, public interest began to wane, and interest in the program seemed over. This discontent, coupled with ABC changing its timeslot on a number of occasions, led to a huge drop in ratings after being one of the most-watched television programs in the United States in 1990. A week after the season's 15th episode placed 85th in the ratings out of 89 shows[...]
ABC agreed to air the remaining six episodes to finish the season. However, due to the Gulf War, Twin Peaks was taken off its usual time slot "for six weeks out of eight" in early 1991, according to Frost, preventing the show from maintaining audience interest. In the final episodes, Agent Cooper was given a love interest, Annie Blackburn (Heather Graham), to replace the intended story arc with Audrey Horne. According to Frost, a female cast member (Lara Flynn Boyle) who was romantically involved with Kyle MacLachlan at the time had effectively vetoed the Audrey-Cooper relationship, forcing the writers to come up with an alternative. Sherilyn Fenn supported this claim in 2014 interview, stating, "[Boyle] was mad that my character was getting more attention, so then Kyle started saying that his character shouldn’t be with my character because it doesn’t look good, ’cause I’m too young. ... I was not happy about it. It was stupid." The series finale did not sufficiently boost interest, despite being written to end on a deliberate audience-baiting cliffhanger, and the show was not renewed for a third season, leaving the new cliffhanger unresolved.
Lynch expressed his regret at having resolved the Laura Palmer murder, stating he and Frost had never intended for the series to answer the question and that doing so "killed the goose that laid the golden eggs". Lynch blames network pressure for the decision to resolve the Palmer storyline prematurely. Frost agreed, noting that people at the network had in fact wanted the killer to be revealed by the end of season one. [...] Looking back, Frost has admitted that he wished he and Lynch had "worked out a smoother transition" between storylines and that the Laura Palmer story was a "tough act to follow". Regarding the second season, Frost felt that "perhaps the storytelling wasn't quite as taut or as fraught with emotion".
Então, resumindo:
- Após o mistério principal de dirigir o show (o assassinato de Laura Palmer) ter sido resolvido e a ABC continuar mudando o horário, o público perdeu o interesse e houve uma queda enorme nas avaliações;
- A Guerra do Golfo foi o centro das atenções e o programa foi frequentemente antecipado;
- Feuds entre os atores sabotados storylines;
- O co-criador Mark Frost admite que a segunda temporada teve uma trama mais abrangente e menos focada.
Tudo isso levou o show a ser cancelado depois de terminar em um cliffhanger.