The most likely reason why Americans turned conservative in all of these ways was because they were engaging in a backlash against the liberalism of the 1960s. In general, political trends like this tend to oscillate. For example, in the 1950s, people were very conservative, which led to a liberal backlash in the 1960s. This is a trend that has happened more than once in American history.
In the 1960s, the US became rather liberal in many ways. Economically, the government started to spend more money than ever on social programs. President Johnson announced his “war on poverty” that was meant to have government programs end poverty. Even President Nixon, a Republican, did things like trying to freeze prices. These are very liberal actions and they led to a backlash later on in which people wanted lower taxes and less spending. Socially, the 1960s were extremely liberal with the Civil Rights Movement, the counterculture, the “sexual revolution” and many more things like that. People, particularly those with more traditional values, rebelled against this trend. Politically, the same thing happened. Americans felt that the country had been dominated by liberals for long enough and so they became more conservative than they had previously been.
This move towards conservatism, then, was a backlash against the liberalism of the 1960s.