It's possible that these viruses jumped to humans all the time in the past and killed a particular village, town, city. Now we have global travel enabled by planes/cruises/cars. The spread is what's killing us with this latest pandemic.
Now you have more than a billion people poaching rare animals to extinction because of superstition, in totally unsanitary wet markets that, frankly, have no place in a modern country.
Nothing had to change. We've had plenty of pandemics before. Black death, 1918 flu, smallpox, cholera, and so on and so on and so on and so on. We're at an all time low in infectious disease deaths in human history - so if anything it's gotten way better thank to vaccines and public sanitation/health efforts.