Some things we do not know for certain. In fact, science estimates mankind has less than 1% of all knowledge.
Dinosaurs could’ve destroyed themselves. How and why they became extinct is really irrelevant to the repetitive nature of man’s problems today. All will be known one day.
Some theories:
Smoking
Driving SUVs
High fructose corn syrup
I'm not necessarily doubting you, but your statement leaves me with two questions;
1) Can you cite your source?
2) Is this the same science you discount with respect to evolution?