Uhm, what attempts to change things did Louis make?
He and the people he appointed attempted finance reforms that were blocked by the nobles. He was by no means great at his job but what went wrong leading up the the Revolution is much more the fault of the nobles than anyone else.
As for Robespierre, principled? He went from being opposed to the death penalty to The Terror. That is a leap even Evel Knievel would have a hard time making. He may have been a fantastic speaker, but he was without a doubt a horrible person who has much more blood on his hands then Louis.