Politics is little more than group conflict fueled by motivated reasoning (i.e., self-serving bullshit). However, it is possible to know some things. For example, financial institutions which are too big to fail are too big to exist. Corruption exists. Powerful special interests, including financial interests, really are powerful. Existing institutions like the Federal Reserve and the U.S. Treasury consistently represent and defend those interests.
On these issues, Bernie Sanders among the candidates comes closest to engaging with reality, though he is also a starry-eyed idealist.
And because Bernie understands that financial interests are powerful, and corruption exists, he must be attacked over and over again by those carrying water for those interests. Of the literally hundreds of attacks made on Bernie in recent weeks, I've chosen just one to make this point. It's a CNN Money article called Janet Yellen disagrees strongly with Bernie Sanders. Here's the lede.
Add Federal Reserve chair Janet Yellen's name to the list of people who wonder if Bernie Sanders has all the facts down on Wall Street regulation.
That link goes to a CNN Money article critical of Sanders called Sanders feeling media heat after new interview. Read that for background. It seems that Bernie was a little vague about the current financial regulatory environment and didn't have a detailed plan for breaking up the big banks.
Bernie's lack of wonkish knowledge is deployed as cudgel to beat him about the head with. (What a terrible sentence that is, but I do like it.)
As propaganda techniques go, this is rather crude. But let's deconstruct it anyway.