It used to be that all geology was defined by uniformity. That is, things have pretty much plodded along in the past, the same way they are now. So, if you see a mountain range being eroded away now at 1 cm/year, all the ancient mountain ranges were eroded at a similar rate.
Uniformity was a really big thing, following the catastrophic 'Noah's Flood' theory. The concept of taking millions of years to raise and lower mountain ranges helped Darwin immensely.
But then this became too boring for geologists. They brought back catastrophe. It's very sexy to think that one day before 'the event' all the dinosaurs were perfectly thriving and happy, then all of a sudden BLAMMY!! The same with the Permian extinction. One day all happy, then the 'DEAD ZONE".
This is much more dramatic than climate changes brought along by tectonic plate movements. Perhaps the dinosaurs and the Permians were dying over millions of years because of everyday things. Who would go to see that in a movie?