Mussolini didn’t actually even make the trains run on time as the old saying went. He did, however, seriously undercut Operation Barbarossa by sheer incompetence in invading Greece without Funny Mustache Man’s OK. It took a couple of Panzer Corps out of the Soviet effort to dig Mussolini out of that one. Should we celebrate the guy’s sheer buffoonery? He did throw Antonio Gramsci into prison, though, so there’s that...
It delayed Operation Barbarossa by six weeks. They might have made it to Moscow by winter if they had stuck to the original schedule.
The world would have been better off if he'd have had Gramsci shot right away.
“He did, however, seriously undercut Operation Barbarossa”
Not really, The German Army wasn’t ready, they hadn’t got all their vehicles yet, and there was severe flooding of the rivers. They had to wait for the rivers to go down.