I think most 'politicians' are upset trump won.
Breaks up the monopoly they had on the office
Certainly the permanent political class, of which Presidents Bush 41 and 43, both of whom I like personally a great deal, are a part of, are going to try to undermine and/or destroy somebody who dares to shake up a status quo that has so greatly benefited THEM. The permanent political class has long been interested only in promoting their personal power, prestige, influence, wealth. The only difference between the parties is the constituencies they represent and they throw those constituencies just enough bones to keep us voting them into their very lucrative positions.
And add in the fact that Candidate Trump said something uncomplimentary about their family member, and it becomes even more personal.
Tacky of them to attack a sitting President.
But typical in a book written exactly for the purpose of doing that.