You write that "in a democratic system" debt grows without a check. Now China which is not democratic shows a high debt on your graph there. Two European countries are in green though. It seems to be something correlated with modern governments rather than a particular governance system.
Another problem I see is peaceful governments in the ancient past were simply annexed by another set that did have a high war budget. It is a kind of tragedy of the Commons.
No it's mostly related to demographics & inner factors. How many old/young people, how many employed/unemployed, how militaristic a country, etc... Europe is very socialist because it's full of old people that need pensions. I don't know about asia, but it seems to have plently of young people there. Less debt = more opportunity there. It seems like the western world has falled through debt.
That sounds like an oxymoron, you can't have a peaceful government that is forcing you to pay taxes. However a limited government was definitely overrun by authoritarians in every case.