yeah, the diastasis is due to pregnancy (not the c/s). Although most mamas will have one, with the first babe it's usually small and many mamas don't even notice it. But each pregnancy will pull those muscles further apart (one reason mamas tend to show sooner with later pregnancies) and stretch them further. A c/s just makes it harder for the diastasis to mend on it's own.
Actually, there are some OBs out there who will add a few sutures to the muscles during the c/s to begin moving them together, but that seems a bit over the top to me! And I can't imagine it makes the general c/s recovery any easier or more comfortable.
I hope everyone is healing well and feeling better!