Which is inline with continuity from Enterprise that the warrior caste was seeing a growing in power, indicating other segments of the Empire also existed.
On a related note, since I've just watched ENT in its entirety, there's something I picked up. There are different factions within the Klingon Empire who aren't on the same page. The Suliban wanted to destabilize the Empire, but it seems as if that destabilization was already on its way to happening anyway. So not only are there different castes, but different wings and different lanes within those castes.
Which ties into the beginning of DSC. Things must've fallen apart shortly after ENT and the Augment Virus probably didn't help matters. So the Klingons were in too much disarray for the next 100 years to be of any threat to Earth or the Federation, which then gave the Federation time to grow.