According to billboard, Damn is the 2nd biggest rap album of the 21st century in terms of pure charts performance. GKMC is also the longest chartin rap album of all time.
So yeah, what kendrick is doing commercially is nothing new...matter of fact, the last 2 times drake and kendrick dropped the same year, kendrick album outsold drake's... drake was only winning as far as numbers moved by their entire catalog, and that's only because drake released more than twice as many material as Kendrick lol.