Jung brought into psychology the notion that things tend to turn into their opposite (https://en.wikipedia.org/wiki/Enantiodromia) as well as the concept of the (psychological) shadow.

The question raised in the article of how could such "deeply ethical people" be "so close to such a massive ethical lapse", is less paradoxical in this light. The same phenomenon shows up with the Effective Altruism movement, and of course lots of other things that present themselves as extremely good.