Because he is effective and is willing to do whatever it takes.
I think they hate him because every politician other than him ascends to office with money and favors used to exert pressure to tow the line. They have no such leverage against DJT.
I think MeneMeneTekelUpharsin's reason for virulant Trump hate is entirely valid, but it's compounded by what you point out, his effectiveness and the willingness to do what it takes! It's the old "adding insult to injury" thing! Obvious in the drumbesat of hate towaerd Trump, is a callous disregard for the good of the country.