I think it’s foolish to think intelligent life never evolved until humans, 66 million years since the KT event and humans evolved recently whereas the Cretaceous lasted 79 million years. Perhaps the were an advanced civilization that hid till the extinction event was over? And maybe they never returned to living on earth cause the environment changed making it no longer suitable for them and they never adapted due to being sheltered in their own locations. Their biology seams more reptilian in nature and during the Cretaceous reptiles were dominant.

Also do you think it’s possible that this civilization reseeded the earth after the event? I always thought that Noah’s ark/book of Enoch/ the watchers were just archaic descriptions of the K-T extinction event transcribed by people that couldn’t comprehend the scientific details of it. Since the somewhat mirror the above idea. Also a lot of religions share a similar flood myth.

Bonus discussion: K-T asteroid impact wasn’t from an asteroid but from one of their weapons and they caused they destruction of earth. Wich would explain their tendencies for anti nuclear weapons.