Why would they fire Corrales and not Acta? Doesn't Corrales do 50% of the strategizing? This seems like the old cutting off your nose routine.
The coaching staff under Acta has been made up of Randy (who was a holdover), Corrales (who was an Acta suggestion when required to have an experienced bench coach), and all of Acta's buddies. The buddies are now gone. Randy was retained, and Corrales is barely mobile and probably needed to retire anyway. To me, this all makes perfect sense. With a young manager, they allowed him to bring in his friends to get his feet wet, plus they were really cheap. Now that Manny has a couple of years under his belt, he needs a real staff, and if the FO is ready to spend money on the big club, they don't want their money going to pay people like Tolman, Harris, and Aponte. Time to bring in professionals.