Two Greek words for "temple":
hieron: The Temple buildings, outer courts (entire temple precincts).
naos: Used in reference to the holy place and most holy place of the temple in Jerusalem, and in Christ's reference to His body as the temple.
The last time the Greek word naos is used in reference to the temple in Jerusalem, is in the verses describing the tearing of the veil between the holy court and the inner court ("holy of holies").
Thereafter it's only used when Paul refers to our bodies as the temple, the congregation of believers as the temple, and in all the Revelation's references to the temple in heaven
- unless the verse speaking about the "temple" which the man of sin will seat himself up in and the verse in Revelation where John is told to measure the temple of God, are the only two exceptions.
hieron continues to be used throughout the New Testament in the (multiple) references to the temple in Jerusalem in Acts and the epistles and even once in reference to the temple of Diana.
The Greek makes a clear distinction between the two.
It makes it highly possible that the "temple" which the man of sin seats himself up in, is an apostate Christian one - and whether this refers to his own body or to an apostate church I don't know. There are only two people called "the son of perdition" in the New Testament: Judas Iscariot, and the man of sin. Judas Iscariot was thought to be not only a disciple of Christ, but one of the inner circle. We are told that Satan entered into him.
Only Christ knew all along Judas would betray him. To all the other disciples, Judas was a faithful disciple and one of the inner circle.
I have not made up my mind about which "temple" the man of sin will seat himself up in. I don't believe anyone knows (yet).