Abiathar went up - i. e., continued to ascend the Mount of Olives. Abiathar was high priest 1 Kings 2:35. Perhaps Zadok is addressed by David 2 Samuel 15:25 as the chief of those who were actually bearing the ark.
Related Commentaries of 2 Samuel 15:24
2 Samuel 15:24
24 And lo Zadok also, and all the Levites were with him, bearing the ark of the covenant of God: and they set down the ark of God; and Abiathar went up, until all the people had done passing out of the city.