These cycles take approximately 5 years. In other cities, there might have been a 100% tear-down, but in Boston, there has to be an attempt to remain competitive while building up the farm. That attempt to remain competitive has to be within the parameters of keeping long-term sustainability the priority. That usually means no big free agent signings. If you're lucky, you can get to the playoffs, or even win a WS during that "rebuild" time.
IMO, both Cherington and Bloom were at the point where the team was ready to go for it. Neither got the chance to see their hard work come to fruition. I was not a fan of Dombrowski, but I do like Breslow.