The "office of the papacy" is the antichrist - a system by which popes stand "in the place of Christ" or "in behalf of Christ" or "instead of Christ".
That's what "antichrist" means.
"Antichrist," in context, refers to how the Apostle John meant it in 1 John. He was referring to the "Little Horn" in Dan 7, where that man poses as an adversary to God's Kingdom and to the Son of Man who comes from heaven. He attempts to subvert the morals of God's Kingdom, and as such, is viewed, by John, as the "Antichrist."
Yes, the "Man of Sin" seeks to have his own edifice built in his own honor, a "temple," of sorts, whether literal or not. I think his claim to Deity is a metaphorical posture, "standing in God's Temple in heaven."
In the book of Revelation we read of 2 Beasts. We know from Dan 7 that the Beast is the 4th Kingdom. But I'm not sure why a "2nd Beast" is mentioned in the Revelation.
It is that 2nd Beast that appears to be the "False Prophet," and may be, in my thinking, a bad Pope, who completely abandons traditional Christianity to worship the Beast as god.
The Reformers didn't base their ideas on current events, but on HISTORY - hence, "Protestant Historicism". The Biblical evidence which establishes the papacy as "antichrist" go all the way back.
The Reformers in their time were dealing with "current events," ie the present existence of bad popes. It is only "history" from our pov.
The proof that the Antichrist arose long ago in history is right there in Daniel, which says the "Little Horn" Antichrist will pluck up "3 of the first horns" which came and attacked Rome.
If you view "Rome" as an extensive historical imperial tradition that ends with the coming of Christ's Kingdom, then "3 of the kings" may not yet have been defeated by the Antichrist.
History confirms that the papacy had the Heruli, the Vandals, and the Ostrogoths wiped out, accused by the papacy as "arian" or "disbelieving in the divinity of Christ".
God wants Jews to be saved - what He doesn't want is the Church handing over to Israel the titles and prerogatives He's bestowed up her after His permanent rejection of Israel.
Paul said that God has *not* permanently rejected Israel. What He has rejected is their use of the Law as a means of national Salvation. And He is presently keeping them under punishment, as a nation, until final judgment separates the sheep from the goats.
Everyone has to decide for themselves: either the Antichrist is the papacy, or a past or future antichrist which exist to deflect attention from themselves.
Yes, we have to form our own opinions, and follow our best sense of what fits God's word.