How did Napoleon lose in Italy?

Napoleon gets back in control of France after his escape from Elba in 1815. He's coming up against a coalition of the UK, Austria, Prussia, Russia, etc. It's at this point that Marshal Murat is in control of Naples. I understand that he tries to invade Austria-controlled Italy, but gets beat at the Battle of Tolentino in 1815. I don't know much more beyond that because I don't have much access to information beyond Wikipedia. <br><br>What are the reasons that Murat lost Italy so quickly?