TPM Cafe's M. J. Rosenberg provides a letter written by his nephew (Jeremy Gruenbaum) to explain it. The kid says "Blame it all on the baby boomers!" I think he gets a lot of the history right, and I lived through most of it myself.
The key point he makes is that the middle class in America suffered through the Depression, then fought through the most massive war the world has ever seen, and came out on the other side of all that into the 1950's. They felt they deserved the America of the 50's in which they quickly became the richest nation on earth. They knew things could get worse and didn't want to lose what they felt they had earned and go back to the massive struggles they had passed through to get there. Instead they wanted to preserve and pass the rewards they felt they had worked so hard for on to their children. The result was a growing conservative movement that objected to the changing American society and who wanted to return to the halcyon days of the 1950's. The result was the conservative movement that effectively took over the Baby Boom generation and won elections.
Gruenbaum makes a number of very good points. I strongly recommend that you go read the entire post. It is food for a great deal of thought. It also delights me that this is an explanation for the political disaster which has over taken America that does NOT blame the DFHs of the 60's and early 70's.
[Gruenbaum wrote his piece in partial response to an excellent piece by Noah Millman in The American Scene. It, too, is worth reading.]