The beginning of the end of The Big Bang Theory can be traced back to Sheldon and Amy’s engagement. After several years of dating that involved a brief breakup and eventual reconciliation, the couple finally took their relationship to the next level as they became engaged to be married at the start of season 11. It didn’t take long for them to tie the knot as much of that year was devoted to the pair planning the wedding. As great as it was seeing Sheldon and Amy going through this journey, this also played a part in the abrupt end of The Big Bang Theory.
Just several weeks before The Big Bang Theory season 12 debuted, it was announced that the sitcom was ending. This came as a surprise since not long before that, talks about ordering another year were supposedly going on internally in CBS, which made sense considering how the show continued to rake in ratings. Despite an uneven final 24 episodes, The Big Bang Theory was surprisingly able to deliver a satisfying and emotional finale. Still, given how crammed its last season was, it would’ve been better if it had at least another year to wrap everything up properly.
While the decision to end The Big Bang Theory was confirmed just before it debuted season 12, it was something brewing for a while. CBS was more than willing to greenlight another year and spend a lot of money for the cast’s salary because of its enduring popularity. But despite the lucrative deal, Jim Parsons wanted out. The actor had been playing Sheldon for more than a decade and for him, they’ve fully explored the character resulting in him losing interest in the show. By the time the star decided this, Sheldon had already gotten married to Amy after a season-long engagement. If the show makers didn’t pull the surprise proposal for Sheldon and instead, took things slow with the couple, then chances are that Parsons still had something to look forward to in terms of his character’s arc in the series.
In an interview, Mayim Bialik said that when Sheldon popped the question at the end of The Big Bang Theory season 10, the writers weren’t sure yet what Amy’s response was going to be. As heartbreaking as it would to see her declining his offer, it would’ve stretched the show’s run. Instead of rushing their wedding, the sitcom could’ve taken their time by developing other characters’ arcs. Raj, for example, had been essentially a supporting player in the last several seasons. Granted that he was given a romantic arc in season 12, that didn’t really go anywhere; despite him and Anu seemingly compatible with one another, suddenly they decided to call it quits. Leonard and Penny’s ridiculous pregnancy story put them in similar, albeit slightly better circumstances.
So while Sheldon and Amy’s story was fully fleshed out, hence why Parsons felt that there’s nothing really left for his character, things were different from the rest of the Pasadena gang. Had The Big Bang Theory paced itself and didn’t fully go on the Coopers’ story, perhaps the actor remained interested and stayed in the sitcom for a few more years. As revealed, everyone else was interested in reprising their roles for season 13 except for him, however, they decided not to continue the show with an incomplete cast.