Among the many mistakes Herr Hitler made, this one had to be one of his worst. [declaring war on the US]
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I agree.
But I think his other biggest mistake — tied for #1 with the declaration of war against US — was not listening to Rommel after France.
Rommel basically said: your next move should be the Suez and beyond. Let’s make the Mediterranean a German Lake and let’s ensure a supply of oil. But I’m going to need major military resources.
Instead, Hitler scrimped on resources for Rommel, wrecked his Luftwaffe over Britain, destroyed his armies in Russia and proved to the world what the German General Staff always knew: he was just a hot-headed corporal who made some early bold moves against temporarily weak-minded enemies.
“Hitler scrimped on resources for Rommel”
I rather think the Royal Navy (Taranto) and RAF had something to do with that. The Germans were relying on the Italian Navy and merchant fleet to move the tonnage that Rommel needed each month. Neither was up to the task. The Afrika Corps was was basically only 3 divisions plus the Italian contingent. And for all their efforts the Luftwaffe & the Italian merchantmen were unable to keep them re-supplied.
There is also the lack of port capacity along the coast of North Africa. Rommel rolled the dice to capture Alexandria long after he had lost the capacity to do so. All his supplies were coming from Tunis, hundreds of miles to his rear. None of the ports between Tunis & Alexandria could handle the tonnage.