Once upon a time, I could not fathom how Hitler rose to power. I read the books. I watched the documentaries. But I couldn't understand how everyday people let such obvious evil flourish.
Intellectually knowing the reasons - such as stoking amorphous fears and scapegoating innocent others - wasn't enough.
Regretfully, I think I finally understand how such things come to pass. And it saddens me that we, apparently, need to learn this lesson first hand every few generations.