He has been all over the political spectrum and managed to garner 10,000,000,000 out of it.
He does what he wants now. He isn’t kissing ass or taking money.
Why does the establishment hate him?
Answer it or go away.
If I may take a shot at answering your question:
The “establishment” hates trump for many reasons.
He has attacked the republican party, not just for going along with Obama for two years, but essentially stacking the GOP for the last 15+ years.
His attacks on W. Might have been meant to stop Jeb, but they also hurt everyone who agreed to go into Iraq and used democrat talking points. He did not attack from the right, but from the hardcore left.
He made many enemies.