Dinosaurs went extinct because of lesser oxygen levels due to global warming.

I know the research is impeccable in timing as it relates to why the dinosaurs didn't evolve. But as one Nat GEO documentary clearly showed with the help of animations that they went down because of lesser oxygen levels due to global warming and it worsened after the fall of asteroids from space which engulfed the world with clouds of dust and led to lesser oxygen levels. Another documentary clearly explained that the oxygen levels during the Jurassic period was approximately around 29% and after the natural calamities it went down to 18% percent which recovered back to 21% after things settled down and that's why they didn't have a chance of surviving while mammals having smaller bodies were able to evolve with 21% oxygen fine.

These theories are not mutually exclusive.