They were never bigger. It's always been one owner and a couple of helpers (inc. Carol of Caroldiva), and currently the owner's assistant, who is also her sister.
The MPRS are, of course, individual sellers, with their own separate reputations and practices. They just have to all meet certain criteria for authenticity in what they sell--but customer service and condition of the goods does vary widely. It was originally a pretty small group that was very carefully monitored. There are still excellent sellers in that list. The authentications by MP is a totally different branch of the organization.