Where did someone assume that the programmer was to blame? How do you find out if the High On Totem Pole Man is to blame if you can't depose the Low On Totem Pole Man? You can't. You are forced to take the High On Totem Pole Man's word for it.
I agree higher-ups bear the brunt of responsibility, but the title of this post currently says "the programmer behind the THERAC-25 Fiasco was never found"
Engineers at VW were found guilty:
https://www.wsj.com/articles/volkswagen-engineer-sentenced-f...