It is a simple case of what I call "the human condition": ignorance compounded by arrogance. It is this that results in what you see in this tragic video.
And, you know, there are an estimated 2,000 or more captive cougars in Florida and most are declawed. Because people like to keep a cougar as a "pet". Cougars are not meant to be pets. I guess they see a nice cougar cub that has been stolen from their mother in the wild and the new owner's first thought is "let's declaw". Horrendous isn't it?. Then the cub becomes an adult and their second thought is, "let's get rid of it".
These people don't think.