Of what is the establishment terrified?
The same as the Republican establishment - they don't want an anti-war president in power. This is why they spent 3 years trying to remove Trump.
Our government is no longer pro-business, it's pro war, exclusively. 10 billion dollars for a wall? Gee whiz, where can we find the money? 1 trillion dollars for a war, no problem. It's been this way since Neocons took control of our government under George H. Bush.
It's a mafiaocracy, not a republic.