The Russian campaign was in 1812 and 1813; he was barely able to extricate himself in the east, and returned to France outnumbered 3:1. He was forced out of power in 1814 (one year, not years later), and returned from his first exile in 1815. In the space of three months the allies brought their armies back into theater, Napoleon threw together one last army, and went on the attack against a numerically superior enemy that was already dug in. He wasn’t able to dislodge them before the Prussian army arrived on his flank.
Which is why he should have been executed to begin with.
ditto all such tyrants that follow
But Napoleon had at the Battle of Nations another army of 400,000 men in 1813 immediately after his battle in Russia.
Certainly Russia happened first. Certainly his defeat at Waterloo happened afterwards. I don’t agree that it was cause and effect. Other things happened in between that hurt him more proximately. His need to divert forces away from Waterloo to suppress a royalist insurrection were at least as important as the losses in Russia, that were, at least half of his losses were not French at all, but allied forces.