I think the fact that steadily increasing tax rates over the decades before 1974 also coincided with high economic growth is a good point against libertarianism.
And the fact that tax rates have been quite high since the early 70s, and yet Sweden's share of the global economy has been basically constant, is also interesting. Libertarianism would suggest that should not happen, and yet it works just fine.
I think avoiding being clobbered by World Wars 1 & 2 was the most important thing :). Probably "neutrality" or "non-aggression" is a better word than "pacifist".
Good points about Sweden having a liberal economy other than high tax rates. I agree that has worked well for Sweden.