It means he steps into the 3rd temple, in Jerusalem, stops their sacrifice, and claims to be God.That's exactly what the scripture says.
II Thessalonians 2:4 "Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God."
What part of the above are you missing ?
That has nothing to do with your interpretation of it, which is simply wrong.