Hitler was taken by surprise at Mussolini's invasion, and was absolutely furious.
http://www.history.com/this-day-in-history/hitler-furious-over-italys-debacle-in-greece
Hitler knew the implications of Mussolini's invasion of Greece and was stark, raving mad about it. You're correct, Hitler bailing out Italy delayed his invasion of Russia by a length of time which proved to be critical.