It was warmer when the dinosaurs roamed because there was a lot more CO2 in the atmosphere at the time. That concentration had been slowly decreasing, becoming oil and coal … until very recently when we’ve been returning it back into the atmosphere.
Just because the dinosaurs were happy under warm conditions doesn’t mean the current world order wouldn’t have significant problems if the current temperature rises a few more degrees. The dinosaurs were adapted to that environment and we (and our civilization) are adapted to this one.
After rising from the last ice age, the temperatures had been pretty stable or very slowly decreasing again (like half a degree in 1500 years) … that is until the late 1800s.