How did behaviorism become such a dominant theoretical basis for education and training in the United States?

How did behaviorism become such a dominant theoretical basis for education and training in the United States? What is changing in the way we think about people and their learning?

The scientific or positivist philosophy of education argues that knowledge can be discovered and constructed scientifically. Positivists assume that we can discover the truth about the world, and that everyone needs to work toward knowledge of the same, ultimate truth, regardless of the topic or field of study. In what ways does behaviorist theory support this  ?