I've always said that were the dinosaurs in fine fettle, they would have recovered from 'whatever' global events. They always did before.
But they had a lot of problems: egg stealing mammals, and they were getting cold (not so hot, get it, huh?). Sooner or later, people will understand what I've been pushing over the last umpteen years, which is that we get massive climate changes when all the plates jam together. The plates act as a giant thermal blanket, and heat up all the subducted ocean crust segments. This pumps out lots of carbon dioxide, but infinitely more important (by orders of magnitude), lots of water vapour. The world becomes hot and steamy, and the plants love the extra carbon.
The dinos are basically just giant flightless birds, like the dodo. They love the heat and get huge. Mammals hate the heat and get small. My huge son is about to take an internship in the Philippines, and he will learn why the tropics don't generally grow huge Viking Barbarians!
When it gets colder, the birds get small, and the mammals get huge. and vice versa.