St. Paul says of “the man of sin,” “the son of perdition, who opposeth, and is lifted up above all that is called God, or that is worshipped; so that he sitteth in the temple of God showing himself as if he were God.” (2 Thessalonians 2:4) These words are interpreted by the Fathers to mean that he will claim divine honours, and that in the Temple of Jerusalem (my comment– even in the Catholic Church). St. Irenaeus says that “Antichrist being an apostate and a robber, will claim to be adorned as God,” and “that he will endeavor to show himself off as God.” Lactantius, that “he will call himself God.” The writer under the name of St. Ambrose says, “He will affirm himself to be God.” St. Jerome, “He will call himself God, and claim to be worshipped by all.” St. John Chrysostom, “He will profess himself to be the God of all, and call himself and show himself off as God.” So also Theodoret, Theophylact, Ecumenius, St. Anselm, and many others.
Suarez, in explaining this passage, says;
It is likely that Antichrist will in no way believe himself what he will teach and compel others to believe. For though in the beginning he may persuade the Jews that he is the Messias and is sent from God, and may pretend to believe that the law of Moses is true and to be observed, yet he will do all this in dissimulation, to deceive them and to obtain supreme power. For afterwards he will reject the law of Moses, and will deny the true God who gave it. For which reason many believe that he will craftily destroy idolatry in order to deceive the Jews.
How great his perfidy will be, and what he will really believe concerning God, we cannot conjecture. But it is likely that he will be an atheist, and will deny both reward and punishment in another life, and will venerate only the preternatural being from whom he has learned the art of deceit and acquired his riches, by which wealth he will obtain supreme power.
“The Pope and the Antichrist”, Cardinal Manning, p. 31-32.