Well...what I'm saying is that basically, the Cardassians in Future #1 threw the baby out with the bathwater.
The one murder wasn't the entire change, of course. But it was the example. Akleen pioneered violent action against authority. He became, through that act, a pack leader of sorts and that gave others a way to act where their instincts might have held them back before. (Just the same as Vetar led people into a less violent sort of protesting.)
They were also desperate because of the horrible things happening to their planet. Though I WILL make the point that I am not necessarily in agreement with all that some say about global warming. The Cataclysm was actually a natural event along the lines of what we experienced on Earth during the Permian-Triassic extinction (the Great Dying). The Cardassians just had the horrible luck to be alive to understand what was happening to them during this period in their planet's development that may well last for as long as their race lives.
The Great Dying on Earth is the time when Earth's therapsids died, all but the direct ancestors of mammals. It is no accident that I chose this to be the form the Cataclysm took: I classify the Cardassians as therapsids--neither reptile nor mammal.