Bruce "Butch" Cassidy was named as the head coach of the Boston Bruins in 2017, after being with the Providence Bruins for 8 seasons. During his time as the Bruins' head coach, he helped the team multiple times to the playoffs. However, he was fired from the Bruins during the offseason in 2022. The year after they got rid of Cassidy, the Bruins were able to break record after record in the NHL.
Some of the highlight records include: Fastest to get to both 80 and 100 points, an overall save percentage of .931, and won 65 games during the season. However, it was the Golden Knights who won the Stanley Cup in 2023 over Florida.
What If Cassidy Wasn't Fired?
If he stayed with the Bruins, it's possible that he could have pushed them to a championship, due to his past success with making it to the playoffs. During this time (2021-22 season), some of the most well known Bruins players were playing, including Brad Marchand, Patrice Bergeron, and David Pastrnak. It also could have given more time to improve more of the players during that season to make them even better than they were.
Keeping Cassidy could, on the other hand, not have helped at all. It's possible the team could have stayed exactly where they were, which was getting to the playoffs but not winning. Making the playoffs is a big deal, but with never moving past the first or second round, doesn't help a team win.
Even though the Golden Knights won the championship right after gaining Cassidy, it was not necessarily due to his coaching style. He had a team that consisted of pretty good players, that had pretty good standings going into the season. The outcome of the 2022 season could have been due to the players themselves, not just the coaching style.
The overall thinking process with this hypothetical, is that it's like comparing apples to oranges. There are many variables that play into this topic. What if the players on the Bruins got even better if Bruce stayed? Or what if the Knights had horrible players when Bruce got hired? What if the assistant coaches played into Bruce getting fired? What if Bruce got fired for other related issues? The situation has an infinite amount of outcomes, where no one could predict what would happen either way. Either way, what happened has happened, and we can only hope that this upcoming hockey season will be better than the last!