Or those ships didn't need to be this big. We only saw brief glimpses of them, most details were indiscernible, so they could have been pretty much any size without an issue. I'm fine with the idea that there are some 'battleships' or 'dreadnoughts' in the fleet and heavy cruiser Constitution is not the biggest, but it is a bit weird that there are now four ship classes that are more massive than it. I'm eyeballing here, Crossfield, Nimitz and Hoover are clearly much bigger than the Connie, while Cardena looks somewhat bigger. Walker and Shepard classes seem to be about the same size as Connie, while Malachowski and Magee are clearly smaller.