The Krag bayonet and M1905 bayonet are similar and sometimes will fit the other rifle, but that was not intentional and they were always considered separate weapons. The Krag latch was found to be weak and the M1905 bayonet latch was a completely new design.
"nothing ever comes up about the krag being a mauser copycat...."
That is because it wasn't. The action designs are not the same, the main difference being that the Krag uses two locking lugs but they are not opposite each other. The Mauser 1893 Mauser (some of whose design was copied by Springfield - they never saw a Model 1898 Mauser) has dual opposed lugs, a somewhat stronger system, and can be loaded using clips ("stripper clips") where the Krag could be loaded only with single rounds. The advantage of the Krag system, and why the Army chose it, was that the magazine could be replenished without opening the bolt and thus taking the rifle out of action.