Subpoenas are an investigating tool. It's part of gathering the data. I think you may be confused. It's not in any way a punishment.

Do you think at that point he had it out for Republicans in general? Republican congressmen were appalled by what happened on Jan 6th, and it was only because they thought Trump would just go away that he wasn't convicted in the Senate.

Trying to frame that investigation as some sort of political witch hunt is ridiculous.