Why Do Some Shows Become Boring Immediately After Revealing Their Biggest Mystery?

Have you ever spent an entire season trying to figure out a show's biggest mystery, only for your excitement to disappear almost immediately after the answer is revealed? Sometimes, the mystery is what keeps viewers invested. Every episode brings new theories, suspicious characters, and clues that make you desperate to know what happens next. Have you ever stopped enjoying a show after its biggest mystery was solved? Which show was it, and did the reveal disappoint you or simply leave the story with nowhere interesting to go?