The reason is obvious: he’s an idiot.
I doubt he knew very much about the Bible. I’ve known Catholics who said they asked their priest something about the Bible and the priest got upset at the person who asked the question. A friend, former Catholic, said he was told not to read the Bible. The church would tell what was in it when they decided he needed to know. I think this priest learned more about Islam by teaching it than he knew about Catholicism.