The New Republic's military focus changed dramatically following the defeat of the Empire. They were now interested in maintaining their power rather than gaining it. Because of this the New Repulbic needed a much larger and deadlier battleship. As a result the M90 project was began. The ship is large for a starship, even larger than the Imperial Navy's Star Destroyers. The New Republic needed to design a vessel specifically constructed to battle and defeat Star Destroyers.
As far as weaponry is concerned, all of the weapons on board coincide with existing New Republic technology, which can easily be obtained for constructing these ships. Unlike previous Mon Calamari designs, this vessel is purely a warship, and not based upon passenger liner designs, like the older M-80 class vessels.
Because of the great cost of these vessels production has been somewhat limited.