Two things to learn from the book:
1) The are same people and organizations behind many science related denials: DDT, tobacco, SDI defenders, acid rain, ozone hole, and climate change denial are linked to same group of people. They try to "maintain the controversy" and "keep the debate alive".
2) The usual suspects don't do this just for the money. Sure, they take money from business sponsors, but the merchants of doubt themselves are not purely cynical operatives and money grabbers. There is type of Manichaean paranoia and ideology behind it. It's related to cold war mentality and free market fundamentalism.
George C. Marshall Institute (GMI) was one of the centers of this ideology https://en.wikipedia.org/wiki/George_C._Marshall_Institute