In Some of my summer reading (2020), when discussing James Holland’s The Rise of Germany, 1939-1941: The War in the West, Volume One:

…. while Italy was allied with Germany, it was a net liability rather than an asset. The Italians failed in North Africa and the Balkans, and so Germany had to commit substantial forces to bail them out.

Grant Piper makes the same point, arguing that The Real Reason Germany Lost World War II was that Italy was a German ally.

Germany never needed an alliance with Italy for its ultimate success. Italy provided nothing for Germany strategically. The alliance was made purely out of ideological brotherhood.

In 1941, Germany had to deploy forces to North Africa and Greece to help bolster the flagging Italian military. Sending numerous divisions, including hundreds of valuable tanks and planes, to Greece and North Africa was not in Germany’s plans. Germany was busy planning a hypothetical invasion of England and a broad invasion of the Soviet Union. They had not planned on deploying forces to Africa and Greece.

The other thing that Germany was burdened with after taking on the bulk of Italy’s military woes was a drastically expanded front. Germany had a good thing going with Fortress Europa and those benefits were undone by Italy’s wayward expansion. Now, Germany had to defend frontiers in the Balkans and in North Africa.

In How Rommel Disobeyed Orders and Cost the Axis North Africa Piper argues Rommel’s campaign there was a mistake. His orders were defend the Italian forces that had been beaten by the British, not to go on the offensive. His spectacular successes lead nowhere except to defeat at El Alamein.

…North Africa offered no strategic value for the Germans. What was the end game? Italy had already proved they were incapable of occupying and ruling the territory. Germany had no plans to control North Africa. Studies drawn up for a hypothetical occupation of Alexandria and Cairo by German forces concluded that the plan was not feasible.