The article doesn't say it explicitly, choosing to hint at it instead, but I think a big part of the popular revolt against big, remote establishments everywhere (also see: Brexit referendum polling) is that these institutions have normally made little or no effort to self police, or demonstrate any kind of ability to self discipline or self reform. The past 15 years especially have seen a more or less constant stream of scandals where people at the top of societies power structures very clearly acted badly or even broke laws, yet nobody was ever held to account ... except those who tried to reveal the wrongdoing. The track record of the elite enforcing the same rules against themselves that they enforce against everyone else is utterly miserable.
This is not a US specific thing. It can be seen to a lesser extent in other parts of the world too. One of the biggest arguments for the UK leaving the EU is that the EU has become a vast bureaucracy that is remote, bloated, undemocratic, disconnected from the people etc. The tone-deafness was made clear when the EU demanded yet another budget rise despite the fact that the member states were all trying to cut their own deficits, often by freezing public sector wages or simply laying people off.
Now mix this in with the partitioning of American society into ever more clearly distinct political tribes and it's not surprising that people who have a message of "We are outsiders just like you who won't hesitate to really shake things up" are getting so much traction. A big part of Obama's original appeal was his entirely unrealised promise to try and reform Washington. Unfortunately he lost interest in that once elected. Not that he could really have fixed anything anyway: the mismatch between emphasis on the US President and how much power they actually have is kind of ridiculous.