My headcanon is this.
I brought this up and of the threads, so pardon me for repeating myself. The last time we saw the Klingons prior to The Vulcan Hello was at the end of the Enterprise duology that established the smooth heads being a result the Klingons experimenting with human augment genetics. At the end of that story, The Klingon doctor played by John Schuck speculated that cranial restoration surgery was going to become a big thing in the Empire.
So, when we see the Klingons a hundred years later with all of these bizarre ridges all over their body, I simply write it off as a Klingon version of body art, like tattoos or piercings. An attempt by a proud warrior culture to avoid being seen to resemble weakling humans.
Of course, I came up with this theory before Strange New Worlds was a thing, and I don't know where they're going to take the story from here, but my head canon is that the augment virus will see a resurgence sometime in the next decade, possibly caused by anti-vaxxers, anti-maskers or general science denial within the empire (ahem), resulting in the Klingons we see in the original series. Whatever cure they come up with this time will restore the Klingons natural ridges making the cosmetic surgeries obsolete.
