The 1964 election was very atypical: many people were still mourning Kennedy, and Goldwater was far from an ideal candidate.
You forgot that a large part of the electorate in 1964 was still composed of the "Greatest Generation's" parents.
And it's still true that the older members of the GI generation had had different experiences from the younger members of the generation.
I didn't have the experiences of either cohort. If I did, I might have voted as they did.