Upvote:11
The actual explanation is two fold:
The island has some German fuel drums. German fuel drums from this time period were galvanized steel and thus have not yet rusted away. The island is not "littered" with them. There is just a small quantity of German fuel drums discarded.
There is more information on the drums here:
http://www.missing-lynx.com/library/german/feuergefahrlichdm_1.html
They were stamped for the service they were intended for, in this case the "Wehrmacht" or German Army. Had the Luftwaffe or Kriegsmarine been supplying this base the fuel drums would be stamped for them.
The Soviet's occupied the island. The drums are stamped 1943. They would have been captured by the Soviet's on the eastern front from the Wehrmacht. They were used throughout the war by the Soviet crews and eventually carried to the island. When you can't get the things you need, you improvise. In this case with captured fuel drums. It's entirely possible that the drums were actually used to hold something other than fuel.
But the German 200 L drums are not likely to fit into a Soviet post World War II supply chain. The dimensions were probably odd compared to the Soviet ones and the capacity probably did not line up. After World War II ended, things like fuel drums were no longer in short supply. The Soviet crews just discarded the drums wherever once empty. Any actual Soviet drums would have been reused.
Of course the exact answer is likely lost to history. But perhaps somewhere in Russia there is an elderly Red Army veteran sitting in his apartment. When he arrived on his first assignment to Matua island, he too was curious about the German barrels and asked the Soviet crews there. Maybe he got an answer from them, or maybe his curiosity was simply dismissed.