So I know the history of napoleon pretty well on a novice level, but marching into Russia just seems like complete idiocy on a militaristic point of view. With the extreme weather's and the russiab army burning everything behind them, he should have noticed it was a doomed attempt.
The only thing I could think of is ego. He could've turned back plenty of times, saving hundreds of thousands of lives. What other possible reason could have left him thinking this shit was a good idea?
Napoleon's central objective in the 1812 campaign was to destroy the Russian army at the Polish-Lithuanian frontier. This hope was evident in his proclamations to his troops that termed the invasion "The Second Polish War" which hints that Napoleon did not want to be drawn into the Russian interior. However skillful Russian intelligence, coupled with a very divided Russian leadership which prevaricated until retreat was the only viable option, meant that the main Russian armies evaded the knockout blows Napoleon aimed at it. In theory, Napoleon could have marched north towards St. Petersburg and the densely populated Baltics, but that would have left an undefeated Russian army at his flanks. So Napoleon opted to chase the Russian field armies culminating in the Battle of Borodino. This bloody battle left the French in no condition to continue the campaign but Moscow was within reach of the remnants of the Grande Armee. Moving on St. Petersburg at this point was out of the question as the distance was too great for the shape the French army was in, so the occupation of Moscow became a false political victory for Napoleon. He thought that occupying this spiritual capital of Russia would compel Alexander I to come to terms, which the tsar would not.