or (2) an actual investigation is a false distinction.It has elements of both.

Political Theatre: Both for Democrats and Republicans. Sessions requested that this be an open hearing because he wanted to make a political case. It was probably smart for him to do so. Democrats wanted him to look squirrly on the subject. Furthermore, these hearings being used for political purposes is nothing new historically; that is poltiics (Benghazi, and to go real old school, the Pinchot-Ballinger controversary).

Real Investigation: I don't think the Democrats were trying to necessarily get new information from Sessions (But I am sure that they would be happy if it happened). What they were trying to do is get Sessions to commit to points. If anyone has done an investigation, they know that this point is just as important as receiving new facts.

Now, my biased thoughts on Sessions:

Substantively, I think it is clear that Sessions and Trump had politically damaging conversations. In other words talks that they do not want the public to hear the light of day about- maybe on pardons, firing Comey, etc.. This is normal in all administrations, and is why executive privilige exists. That doesn't mean the public doesn't have a right to know about this, just that there is also a normative rationale for not disclosing as well.

I also think it highly unlikely that Sessions colluded with Russia. I have trust that a life-long public official would not betray their country just to get a political victory over Democrats. Note, that just because I don't think there was collusion doesn't mean that I don't think other shady things happened.

An investigation is the combination of multiple bricks to form a wall. There have been more than enough reports and actions (both anonymous and on the record) that gives a reasonable suspicion something was going on with Sessions. I think more likely after today that Sessions was only involved in political tom-foolery. But It would be malpractice for an investigator not to even look into it.

Lastly, my personal beliefs could completely change if Sessions committed perjury and there was a different reason for recusal as Comey hinted about.