@Paaskynen,
You raise some good points. I agree that the advent of the atomic age made a worldwide apocalypse more immediate, but that doesn't entirely explain the lack of post-apocalyptic movies prior to 1945. After all, there was
post-apocalyptic literature prior to Hiroshima and Nagasaki, dating way back to the grand daddy of all post-apocalyptic visions, the bible's book of Revelations, and even before that to the tales of worldwide floods found in Babylonian and Hebrew myth.
I wonder if the dearth of post-apocalyptic movies prior to the 1950s has more to do with cinematic limitations and popular tastes than with any sort of unfamiliarity with the genre. Science fiction films weren't very popular prior to the 1950s either, even though some of the first movies ever made were sci fi films:
Having lived through World War I, however, audiences of the interwar period may not have been interested in something as depressing as
another worldwide catastrophe. Also, filmmakers faced limits in terms of the kinds of special effects they could use (although some of the early sci fi films, such as Lang's
Frau im Mond (1929), remain quite impressive). H.G. Wells wrote
The War of the Worlds in 1898, but a film version wasn't made until 1953, at which point motion picture special effects had finally caught up with Wells's imagination. So it may be that post-apocalyptic films caught on after 1950 because they finally found an audience and were finally able to portray a post-apocalyptic landscape convincingly.