Casebolt's career was ended because he manifested an erratic form of behavior which, if they had tolerated it and allowed him to continue, could have negatively affected his superiors' perceived ability to manage. He presented himself as a loose cannon and the bosses have no way of being sure he won't do it again.It's a really simple thing, police are human, of course you have never done anything that seemed right at the time but later regretted it, right? The guy was officer of the year at one time, should one incident where no one was hurt end his career? Demanding perfection of any human will lead to certain disappointment. But then you have a record of demanding perfection of people you disagree with, so never mind.
One possibility is Casebolt has lapsed into a psychopathic frame of mind, which that occupation is capable of inducing.
Another possibility is he's using steroids, or he's been experimenting with methamphetamine seized from a dealer. (Don't think it doesn't happen!)
A third possibility is Casebolt has been a developing screwball for some time now and he's finally overdone it and got caught on camera. There are a lot of bad cops out there who will continue to harm people with their malfeasance and brutal disposition until someone points a lens at them. So the time when they finally get caught is not necessarily their only turn at bat.
You're right, there is no way to be sure because left wing assholes refuse to wait on an investigation before passing judgment, as is normal for the left, they want instant gratification. Real adults are willing to wait and see what is shown in an investigation.