So who was the antichrist who set up as God in the Temple prior to 70AD? And when was Revelation written?
There is no individual "antichrist," since that term includes everyone of every religion (or no religion) that denies Jesus is the Christ. I will assume you are referring to the following passage, since you did not provide a reference:
"Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition; 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." (2 Th 2:3-4 KJV)
If you compare the Greek word for temple, you will find that is the word that is used for a spiritual temple. For example, when Jesus was in the temple, as in Mat 24:1, the Greek word was this:
(2411) hee-er-on’; a sacred place, i.e. the entire precincts of the Temple (at Jerusalem or elsewhere)
When Jesus referred to his body as the temple, as in Mat 26:51, the Greek word was this:
(3485) nah-os’; a fane, shrine, temple: — shrine, temple.
After the book of Acts, the Greek Word nah-os (3485) is used in all but instance of the word temple, when Paul used it in 1 Corinthians in the following manner:
"Do ye not know that they which minister about holy things live of the things of the temple? and they which wait at the altar are partakers with the altar?" (1 Cor 9:13)
Therefore, my interpretation of the Man of Sin is that he received the Holy Ghost; but began to use it for evil, like Judas (both are referred to as sons of perdition.) He got so "cocky," if you will, that he thought he was God, which would make him the spiritual temple of God.
Whatever the case, I would find it most difficult to squeeze a physical temple out of that short passage.
Philip