I agree; the confusions in The Olivet Discourse are a good indicator of the authenticity of transmission of the the NT. If 'people' were just cutting and adding and editing the NT over the centuries The Olivet Discourse would be one of the first passages to want attention? Unless it was deliberately and cleverly constructed later after the destruction of the temple as @Miken suggests? Is there other evidence for a later dating for the Gospel of Mark -- to after AD 70? The abomination of desolation referred to in the prophecy? After the original abomination of desolation referred to in Maccabees and Daniel -- the statue of Antiochus Epiphanes erected in the temple.