Answer:
It’s not really thought that it was just an impact event that caused the extinction of the dinosaurs. In fact, it’s believable they were on the decline well before the impact event came along.
The main contributor before the meteorite was climate change. This was greatly amplified by a massive increase of volcanic activity in that period.
Of course, there are other theories. Plague, food chain imbalances, Vitamin D deficiency, and more.
All we know for sure is there was a massive impact event that occurred during a period of great volcanic activity. Either of which could have caused a great extinction by themselves.