The Swedes that I know don’t believe that their culture or heritage ever had anything to do with Christianity, not voluntarily at least.
Christianity was introduced into their very brutal, disorganized, and heathen culture by nonviolent missionaries, who won Catholic converts solely by their preaching and example: the heroic monks Ansgar and Rimbert, the English missionaries David and Eskil, the German missionary Stephen, and the Swede Botvid.
The Gospel penetrated the hearts of the battle-loving warriors very slowly, since the Christian missionaries opposed drunkenness, raiding and looting, blood-feuds, bride-capture and other violence, polygamy, human sacrifice, and the exposure of children (all very common and indeed popular Native Scandanavian practices.)
Eventually the zealous preaching of the Gospel succeeded, and he first national synod was held I think in the 1100's.
As the Swedes gave up their anarchic tribal violence and the society became wealthier through their new Christian virtues (diligence, frugality, sobriety will get you somewhere), the Church became very wealthy through bequests, titheing, and royal favor. The Church's success ironically led to its corruption: the Church grew slack in morals and fat with wealth.
All this came down in the mid-16th century as the State appropriated Church properties and the Church of Sweden (Lutheran) became, by compulsion, the State Church. There's where the "involuntary" allegiance to Christianity (via the Established Church) became full and formalized. In Sweden, the so-called "Reformation" was a political tool used by the king to secure control over the church and its assets
Now all is pretty much flat, socialist, and secular. The Church of Sweden (Lutheran), which has majority official numbers, is almost entirely defunct.
Interestingly, Muslims make up 5% and Catholics 2% of the population of Sweden, both --- largely through immigration--- are experiencing a period of significant growth.