Afghanistan isn’t the first time a defeated Superpower hastily left a battlefield without their equipment and supplies.
Dunkirk was equally bad.
64,000 abandoned vehicles (including tanks and motorcycles)
90,000 rifles
2,472 field guns or artillery pieces
76,097 tons of ammunition. 
I want this book! Stephen Wynn’s book, Dunkirk and the Aftermath - Rare Photos from Wartime Archives
This article has photos from the book. Amazing history.
The US didn’t leave that much behind actually. Most of what we’re seeing is Afghan National Army stuff, not abandoned US equipment. It just happens to mostly be the same stuff the US military uses.
Keep in mind, that we only had 650 troops in Afghanistan when Kabul fell, so the vast, vast majority of stuff was already withdrawn by then, or was slated to be abandoned anyway.
Yeah, there were logistical issues obviously at Dunkirk, they didn’t really have access to proper loading facilities for equipment. The harbor’s proper facilities had been rendered unusable by German bombing, there was a large protective mole extended out into the harbor that some troops were able to use to directly board larger vessels, but it would not have been feasible to move heavy equipment and material in significant number over the mole. Many of the evacuees had to wade out from the beaches onto the “Little Ships” that then ferried them to larger vessels that would take them across the Channel. Just wasn’t much option or time to worry about all the gear.
I found it interesting that Germany started manufacturing ammo for the English anti-aircraft guns. I guess they were effective weapons.
Compared to what was at that time a modern, mechanized German army, the British equipment left behind was junk. It certainly didn’t benefit the Nazis in any way. The disparity between the allied forces and the German army at the beginning of the war was critical. The Germans had modern fighters while there were still some WWI leftovers in the RAF.
Actually, the Germans made good use of much of the British equipment. Germany was chronically short of military equipment, especially motor transport, all through the war, and any British vehicles not damaged in the fighting or sabotaged by their retreating owners were quickly pressed into service. A number of captured tanks were used for rear area occupation units and many Universal Carriers were modified to carry small anti-tank weapons. Beutepanzer - Wikipedia
Those motorcycles were a deliberate sabotage effort! 
The largest number of horses of any army in history.
AEC Matador trucks, big 4WD babies, were much prized by the Germans, as they had nothing comparable. AEC Matador - Wikipedia