Who is the group of people whose souls were concerned, thinking of Allah other than the truth, with the thought of the Ignorance (Jahiliyyah)? And why is it unlikely that they are the hypocrites? And is it possible that this group was believing then characterized as hypocrites?

Yes, Abdullah ibn Ubayy ibn Salul returned with one-third of the army, and they did not participate in the fighting in the Battle of Uhud. However, some of the hypocrites remained with the Muslims, as indicated by the noble verses in Surat Aal 'Imran, which mention that a group of Muslims was overcome by drowsiness, a security from Allah, while another group of hypocrites were anxious about themselves and harbored unrightful thoughts about Allah, like the thoughts of the Age of Ignorance, saying: (Is there anything for us of the matter?). Then Allah revealed what they concealed within themselves by their saying: (Had there been anything for us of the matter, we would not have been killed here).

Al-Zubayr ibn Al-Awwam narrated that he heard Mu'attab ibn Qushayr say that, and concerning this, Allah Almighty revealed the verse.