Moving on from Fleury and keeping Murray was objectively the right decision, even in hindsight.
Even if you only look at it at what they had done since that decision, which is a really bad way to evaluate trades, it was still the right decision because keeping Fleury would have had dramatic cap consequences. That extra $3.25 million or so between Murray and Fleury had to come from somewhere. Considering how goaltending wasn't even the reason they lost in the playoffs in the last 3 years (Murray was mediocre in the playoffs in each series IMO, not great but not bad), you're spending cap space that they didn't even have available on an upgrade you didn't even need to make.