Olaf II of Norway was officially canonized in 1164 for bringing Christianity to Norway in the 11th Century. Modern scholarship, however, says that he most likely played a minor role in the Christianization of the country. How and why did his role in the Norwegian conversion become so overemphasized?

I think much of the answare to your question can be found in what he is called in Norway, "The Holy". He got this name because after he died he looked just like he slept, many months after his death, his hair and nails apparently had grown just as they would if he was alive. In addition it was said that miracles happened close too him, blind got their vision back and leppers was healed. Acourding to snorre when Tore Hund (Dog/Hound) was tending to the body of Olaf after the battle of Stikklestad a drop of blood from Olaf ran down on Tore's hand and down on a wound he had optained during the battle and it healed so fast that there were no need to bandage the wound. And while Snorre wrote his works after the cannonization of Olaf II it shows what people thought. Acourding to the people of the time Olaf II was a martyr of Christ. They believed that he could protect them from disease and war and give them good harvests. And people went on pilgrimage to his grave in Nidaros (Trondheim) until Norway became protestant. This is the reason he got cannonized and therefore i would say that his contribution in Christianiszing Norway was not overemphasized, it just was not that important compared to the signs and miracles that happened close to him.

I hope that this answared your questions and that it was not to dificult to understand. I am sorry for my english and please ask any questions if something was unclear.