There was a second reason: The RNC and the Rockefeller wing of the party sat on their hands (and wallets). Goldwater got no help, save from his own voters (like me).
There is a definite risk that the GOPe and the RINO wing will do the same thing to Cruz -- leaving it up to his voters (like me) again.
I agree with your recollections. But today I think those GOPe Eastern Wing RINOs are no longer the only go-to funders. I am convinced that should Cruz be the nominee he will attract the wherewithal to fund a fully competitive campaign.
You won’t be alone. There are a lot of Cruz supporters like us who will dig deep to give the most we can, if Cruz gets the nomination.
And reason number three: a popular young president had been assassinated the year before. It was, in effect, JFK’s second term.