Christianity is the real corpus of followers of Jesus and the real teachings they believe and principles they practice (Acts 11:26). They emerged at the first century and they were united in the same beliefs and way they called the truth. They were one group with the same principles until by the second century the Way was hidden by apostates, just as the weeds cover and hide the wheat.
It had already been prophesied that this would happen, but that at the end of the human world system of things, the wheat and the weeds would be recognized and the harvest successfully accomplished (Matt. 13:24-30,36-43).
Paul had said that these apostates had not yet fully developed because there were still alive in his time some anointed with spirit from heaven who prevented their full development, so when the last of them died, the conditions that the Devil had expected were met. to develop that "apostate Christianity" that changed everything.
2 Thess. 2:3 Let no one lead you astray in any way, because it [the presence of our Lord Jesus Christ and our being gathered together to him __ v.2] will not come unless the apostasy comes first and the man of lawlessness gets revealed, the son of destruction. 4 He stands in opposition and exalts himself above every so-called god or object of worship, so that he sits down in the temple of God, publicly showing himself to be a god. 5 Do you not remember that when I was still with you, I used to tell you these things?
6 And now you know what is acting as a restraint, so that he will be revealed in his own due time. 7 True, the mystery of this lawlessness is already at work, but only until the one who is right now acting as a restraint is out of the way. 8 Then, indeed, the lawless one will be revealed, whom the Lord Jesus will do away with by the spirit of his mouth and bring to nothing by the manifestation of his presence. 9 But the lawless one’s presence is by the operation of Satan with every powerful work and lying signs and wonders 10 and every unrighteous deception for those who are perishing, as a retribution because they did not accept the love of the truth in order that they might be saved. 11 That is why God lets a deceptive influence mislead them so that they may come to believe the lie, 12 in order that they all may be judged because they did not believe the truth but took pleasure in unrighteousness.