I agree; Lucius knows Hermione is innocent (not that she didn't do it) and the clue about the Wizengamot fizzled out.

However, I think Dumbledore's preferred outcomes here seem to be the smallest disturbances of the status quo. (Fawkes needs to give him a few more thwacks.) Hermione going to Azkaban disturbs things less than Harry going into debt disturbs things less than Harry destroying Azkaban. So at least there does seem to be a consistent utility function here. (The other, highly improbable, explanation for that preference ranking is that he approves of dementors feeding on innocents in general.)

I think Lucius is mostly grandstanding, just saying whatever will make him seem most like a formidable politician and least like he's backing down.