Jews know something happened. They are just not too precise on exactly what. Emotion tends to override reason for the Jews. Many of them assume criticism of any aspect of the official narrative is an attack on the entire narrative. So, to answer the question, all Jews believe "something" happened that they call the Holocaust, they just aren't really sure what happened. Most of them are terrified to question the narrative, for fear of being labeled "self-hating Jews" which is the label Jews put on other Jews who don't toe the line.