"I want a monocultural Christian Europe" - Anders BreivikThat is because he didn't do it for religious believes, it just isn't the same at all.
"Europeans are culturally Christian, it doesn't matter if you have a personal relationship with Jesus." - Anders Breivik
"I am a modern day crusader." - Anders Breivik
So he believes that all "true" Europeans are "culturally Christian" whether they take interest in the religion or not. He wanted to fight for a "monoculture" - i.e. he believed cultural Christianity should be the ONLY culture in Europe and all other cultures should be pushed out, violently if necessary. And he identified with the crusaders and knights templar, who were Christian warriors fighting for the expansion and defence of their religious beliefs.