the Democrats are too dumb as hell to act on what they already got/gonna get
I don’t think that’s fair to say at all. You’re ignoring the fact that Mueller’s testimony in this public setting is only possible at all because the Democrats control the House and have the power to investigate like this, which is not something the Republicans would ever have done if they still had control. And you’re also overlooking the fact that this testimony allows Democrats to not only push back against the false narrative Barr trotted out, it helps keep the report and its conclusions fresh in the minds of the people. They know as much as we do the Republicans are never going to do anything to hinder Trump in any way and would never impeach him (like they should), so continuing to remind everyone is one of the few things they can use it for at this point.
It may not be the action we want, but it is still action.