Now they can't get him back in his cage.

It is very unusual to see a US political movement disembowel itself in the way the conservatives have done with that decision. What control the national parties have retained was based on the money and access that they could provide, which was already under attack by the various free-lancers and enterpreneurs that usually populate the Congress, and what Trump has shown is that you don't need the national parties for money or access either. They are not required, to play or to win.

I'm having trouble thinking of anyone else who could manipulate the M$M the way Trump has...

I'm also having trouble thinking of anyone who could spread Bernie's message with more credibility.

So in that sense, he's recent and uses tech not available to his predecessors in politics. I expect he will not lack for wannabe imitators.

With Bernie I think your case is bettter, he is at least pretty unusual in US politics.

has origins that go back decades

A systemic cause is something that goes back decades, like you mention. In this case that would be the corrupt taking of money for favors by politicians, which goes ALL the way back. It is the rule, not the exception.

A proximate cause is the thing that set it off, the thing that happened right before, the pebble that popped out right before the landslide started.

Now, in this case: systemic corruption, the habit of taking money for favors, is the systemic cause, and CU is the proximate cause, the thing which set it in motion, which chopped off the last restraint.

Most things have many, many causes, everything is tied together, once you start looking into it. There is always disagreement about what is the "background" and what is the "picture".

And now Mr. Trump, by his good example, will cause lots of imitators.