...the bringing of the bluestones, the bringing of the sarsens, the crazy folly-like design of the monument - and of Silbury - all reflecting the insane ego of leaders.
Of course, if Stonehenge (or a wooden proto-type) were originally on top of Silbury that'd be even more of a crazy folly-like design ;-)
But maybe that's not as farfetched as it might seem. The 'priesthood' at Avebury may have upped camp, or split away, from the existing one and relocated to Stonehenge (that sort of thing happened all the time in Japan, with one capital city after another being moved in order to get away from a too powerful priesthood). The Stonehenge builders may still have had a transmitted memory of a wooden, Stonehenge-like structure on Silbury which was then refashioned in stone at Stonehenge. If there was a split at Avebury (and that's perhaps more likely as a total relocation would have probably involved moving some of the Avebury stones to the new site) the people who left would be hell-bent on proving they could build something better and more durable.
Crazy though, surely they would have known that mortise and tenon joints were not really needed at Stonehenge. Maybe their respect for tradition was such that they didn't want to deviate from what went before. Hell, if they were prepared to drag stony monsters from all over the place a few little mortise and tenon joints on top of them was just icing on the cake (or a bit of showing off).
Anything you can do we can do better... no you can't... yes we can... :-)