What factors led to the decline of Christianity in Sweden?

This is my first time ever posting on a Chambers history sub so I apologize if this type of question has been repeatedly asked before. Firstly, I would like to point out that I am not religious myself and do not hold anything against Christians. I am merely here to learn and ask questions. Secondly, I know that Sweden is not a fully secular nation as around 60 percent of people in Sweden are still Christian. However, I have read that the number of people identifying as Christian in Sweden have greatly declined, with an anticipated 41 percent of the country turning irreligious by 2050. My question is what factors contributed and continue to contribute to the decline of Christianity in Sweden? I have a hypothesis that perhaps the Sweden secularizing in 2000 and allowing same sex marriage may have influenced this, but otherwise I’m not really sure.