In the movie version of Les Miserables, the final scene is the very upper class and opulent wedding of Marius and Cosette. Is Marius completely selling out the revolutionary cause and abandoning all his friends who have died? This point seems to be glossed over in the movie and Marius isn't portrayed in any negative way for this, but in my mind should be very damning of him.
I would suggest he's moved on.
The revolution has bee crushed and his friends are dead. No one's going to rise up for a long time. He can dwell in unhappiness, rebel again (probably by himself and die) or carry on with his life with Cosette.
He chose the latter.