Regarding the connection between APOSTASIA and ANQRWPOS THS ANOMIAS, TDNT makes these comments:
"In 2 Th. 2:3 APOSTASIA is used in the absol. sense as an event of the last days alongside or prior to (?) the appearance of the ANQRWPOS THS ANOMIAS. Here a Jewish tradition is adopted which speaks of complete apostasy from God and His Torah shortly before the appearance of the Messiah. This is applied to the apostasy of Christians from their faith to error and righteousness (v. 11f.) in the last days (Mt. 24:11f.)" (TDNT 1:513).
In the footnote (page 513), TDNT states that APOSTASIA is undoubtedly used of "Christians" in 2 Thessalonians because the word implies a prior turning to God. I might add that the word especially applies to apostate followers of Christ in this context, who are likely nominal disciples of the Lord.
This academic work reckons that the "apostasy" and the ANQRWPOS THS ANOMIAS "are to be differentiated, but only in such a way that the apostasy makes possible the power of the man of sin, and this in turn increases the apostasy" (1:513-514).