I recommend that anyone who's interested in whatever real history may lie behind TDVC read "Holy Blood, Holy Grail", which summarizes a serious scientific inquiry into the subject.
The point is not about the Grail myth, or Leonardo's idiosyncracies, but the systematic suppression and persecution of the female power and symbology (which we inherit from pagan times) by the Catholic Church. It can be argued that no other power grab has been as damaging to the evolution of mankind as a species as the forced change from a matriarchal to a patriarchal society.