Trump is attractive precisely because the Establishment fears and loathes him because 1) they didn't pick him and 2) he might upset the neoconservative Empire that the Establishment elites view as their global entitlement.
The Establishment is freaking out about Donald Trump for one reason: they didn't pick him. The Establishment is freaking out because the natural order of things is that we pick the presidential candidates and we run the country to serve ourselves, i.e. the financial-political elites.
Donald Trump's candidacy upsets this neofeudal natural order, and thus he (and everyone who supports him) is anathema to the Establishment, heretics who must be silenced, cowed, marginalized, mocked and ultimately put back in their place as subservient debt-serfs.
With Trump ascendant, the serfs are selecting the noble in the castle on the hill. Outrageous! Unheard of!
You know the Establishment is freaking out when Establishment pundit mouthpieces like David Brooks and Francis Fukuyama are freaking out about Trump. David Brooks could not restrain his disdain for Trump on a recent Charlie Rose segment, in which he intoned (and I paraphrase) that Trump can't put eight words together without referring to himself, i.e. he is not just a narcissist, but he is (take this, Trump!) a fragile narcissist-- unlike people like Brooks, of course, who are solid, secure, wise, well-educated, erudite water-carriers for the status quo.