Stonehenge

I think that we can accept the archaeological data on when and by whom Stonehenge was built; about the methods used to build it, the proposed solutions will remain speculative but are fairly plausible.
The big question is WHY it was built: again, what idea was strong enough to be associated to a particular area during millennia? and also, what do we know about the social group structure and leadership? Could they manage the effort involved?