As others have pointed out, the purpose of the investigation is to find details on the circumstances and causes of the attack from a bipartisan point of view. Critics of this move often point out the fact BLM riots, which also caused property damage and deaths, were not investigated and thus, they conclude this investigation is purely political theatre.
There is no longer any point in impeaching the former President. It is being convened to answer the kinds of questions the 9/11 commission did: the who, what, when, where, and why of the incident.
Questions I'd expect to be answered:
Who were the first co-conspirators, and how did they recruit?
At what point was it decided (and by whom) that they would ...
The purposes of the Select Committee to Investigate the January 6th Attack on the United States Capitol - according to H.Res.503 which established the committee are as follows:
Consistent with the functions described in section 4, the purposes of the Select Committee are the following:
To investigate and report upon the facts, circumstances, and
Is the purpose of the investigation of the events of January 6th to decide whether Congress should impeach former President Donald Trump?
No, the purposes of the investigation are given in H. Res. 503, June 30, 2021.
H.Res.503 - Establishing the Select Committee to Investigate the January 6th Attack on the United States Capitol.
SEC. 3. PURPOSES.