While I cannot comment on your grandfather...
I don't believe von Braun was ever labeled as a lunatic. That sounds
like a bit of a cliche.
von Braun was handsome, popular, smart, and charismatic (they don't
make geeks like they used to, do they?). His WW2 bosses didn't want
him doing anything with rockets other than dropping them on the rest
of Europe, but his engineering and management skills were highly
appreciated during the war and after by the US.
As I said elsewhere, had we listened to von Braun, not only would we
have had a satellite into Earth orbit before the Soviets, it is likely that
several worlds would have had permanent manned colonies by now.
And a real space station that serves multiple purposes.