I agree that the term "Karen" has its genesis as an insult, and one designed to effectively aggravate the people it describes. It's not surprising to me that it's a word people reach for when they want the impact that words like "asshole" have lost. I don't know why you would call someone an "asshole" if you want to be genuinely mean.

"Asshole" is as common as salt in our everyday language, but "Karen" is the spice.