Eisenhower, it all comes back to Eisenhower.
Truman had done a lot that conservatives disliked. The country had been Democratic for so long, citizens didn't know what the nation would be like without it. They had to have hungered for something new. So that's Eisenhower, whose most enduring legacy (the highway system) is contributing to global warming.
Americans were free before 1950. After that, the Pentagon, the CIA and all of their brothers were invented.