The possibility that Trump would step on favored political toes and act pragmatically to rein in Imperial over-reach terrifies the bloated Imperial city of Washington D.C.
Political scientist and theoretician Joseph Nye, Jr. differentiates between transformational presidents and transactional presidents: transformational presidents consciously set out to radically transform America and/or America's role in the world, while transactional presidents are pragmatists who focus on managing crises and responding with caution rather than taking bold and dangerous bets.
Nye explains the difference in Do Presidents Really Steer Foreign Policy?: George H. W. Bush was a (successful) transactional president, George W. Bush was a (failed) transformational president.
Other historians have drawn distinctions between ideologically driven presidencies (Reagan and Carter, for example) and those who practiced realpolitik--making decisions based on realities and circumstances on the ground rather than on an overarching moral or ideological framework. Richard Nixon is widely seen as a realpolitik president, as were Harry Truman and Dwight Eisenhower.
You see the overlap, right? Ideological presidents are transformational, as the world inevitably fails to match up to their ideals and goals. Realpolitik presidents are transactional, making decisions based on context, risk, and the situation on the ground. These presidents are often criticized for not "saving the world," i.e. intervening to "right" some morally reprehensible crisis, or for not "defending America's interests" more aggressively.
Obviously, every president has a mix of ideological underpinnings and pragmatic skills.
As I pointed out in Sorry, "Feel the Bern" Fans: President Sanders Won't Change Anything, very little of the Imperial machinery is under the direct control of the President, and Congress and the Supreme Court can block a variety of presidential aims.
The mainstream hysteria about President Trump (and to a lesser degree, about President Sanders) is misplaced: rather than be the ruin of the nation, either president would face a number of limits on his power.
Playing devil's advocate here--perhaps Trump would be an extremely transactional/ pragmatist president who would decide everything on a case by case basis. The two political parties and the Status Quo of institutions and Imperial agencies like predictability; everyone likes knowing politicos can be bought off or compromised, and they like ideological presidents because their choices are fairly predictable.
Trump upsets the Establishment precisely because he maintains a freewheeling lack of predictability and vulnerability to the usual blandishments of money and power. Not only can't he be bought, he doesn't toe any ideological line.
Here's a sample test for an effective president: can he/she cancel a big, costly, failed "but it creates jobs" weapons system like the F-35? The political pressure to maintain spending billions on a DOA weapons system like the F-35--$200 billion each, underpowered, buggy and unable to best the aircraft it replaces in unrigged air-to-air combat, even after decades of development and years of "fixes"--is immense.
Hillary Clinton would never cancel such a politically powerful weapons system, even though when speaking privately, every unbiased military advisor would admit it's a complete catastrophe. (Could the Skunkworks design and mock up a better, cheaper aircraft at a third of the cost of the failed F-35? Why not let them try? They did so with the F-16.)
Could President Trump (or President Sanders) take the political heat and cancel the F-35 in favor of a faster, better cheaper replacement that doesn't try to be everything to every service?
The possibility that Trump would step on favored political toes and act pragmatically to rein in Imperial over-reach terrifies the bloated Imperial city of Washington D.C. This is why he is painted as the Devil Incarnate by the mainstream (i.e. bought and paid for) media and both political parties.
A transactional president who would make pragmatic decisions that gutted Imperial over-reach and eliminated failed programs because they are unaffordable and ineffective is dangerous to the Status Quo because he can't be bribed or swayed by the usual siren songs of ideology or party politics.
Taking the other side of the argument: suppose Trump ends up caving in to the usual Imperial pressures. How would that any different from electing Goldman Sachs Hillary? Wouldn't it still be more entertaining and less dreary than four years of completely predictable Imperial over-reach and the protection of privileged financial elites with Goldman Sachs Hillary?
Why Trump and Sanders Were Inevitable: It was only a matter of time before we had a populist backlash to 30 years of flawed globalization policies that both parties embraced.