Uriah

Nazi anthropologists were a bit disconcerted when they discovered that Germans as a people are actually quite brachycephalic. The only section of the country to have totally resisted the trend were the cattle raising people of Schleswig-Holstein

I think the advantage that dolicocephals possessed was that dolicocephaly in North Europeans is actually a consequence of brain overgrowth induced by milk consumption. The lactose tolerant enjoyed a strong advantage in the country that was lost in cities; milk is hard to move.

The trend toward feudalization was probably more decisive than urbanization in the long run. Northwest Europeans preserved tolerance partly because of their low population density but also because they broke away from feudalism early and independent farmers drank more milk.

So why, absent milk, do bracycephalics outcompete the longheads? Well, they're better at everything: they conserve heat more easily, have a higher ratio of brain volume to surface area, and it's easier to for a small, spherical head to stay symmetrical and pretty than a long one.