After hiving been removed from office Abiather is mentioned as priest along with Zadok and Benainh as commander in chief. The order of events in the previous chapter is that Benaiah first killed Adonijah then Abiather was removed from office and lastly Joab was killed.
Benaiah assumes the office of commander in chief after the death of Joab which would have taken place after the removal of Abiather according to the chronology in chapter 3
1 Kings 4:1-4 NIV
So King Solomon ruled over all Israel. 2 And these were his chief officials:
Azariah son of Zadok—the priest;
3 Elihoreph and Ahijah, sons of Shisha—secretaries;
Jehoshaphat son of Ahilud—recorder;
4 Benaiah son of Jehoiada—commander in chief;
Zadok and Abiathar—priests;
So why is Abiather mentioned as a priest after Benaiah had assumed the office of commander in chief, and Solomon had banished him as per 1 Kings 2:27?