'Yes, but which establishment? It seems that there are many different establishments going around...'
I don't know exactly how it works. there are different competing forces of billionaires and oligarchs. The Establishment is not set in stone, it changes over time as power changes, the Establishment is only the forces that are currently more powerful at any point in time than their competitors.
Trump is competing to overthrow them, he is outnumbered and overpowered by them but he is giving it all he has got on the campaign trail and using the people to turn out and vote which will end up busting up the current Establishment.
As Robert Reich, Bill Clinton's former Labor Secretary, wrote
"the establishment is dying"
it is being challenged by Bernie and Trump, but it is using Mitt Romney and all its servants to try and stop itself losing power.
The next round in this struggle for democracy and freedom is tonight. Tune in to find out if Trump beats them and gains the upper hand.