I don't think that it has to do anything with time. Football is very popular in both Japan and South Korea, and this has been the case for the past decades. I am not exactly sure why the Asian teams underperform at international level. Despite their huge population, China and India almost never qualifies for the World Cup. Asian players are in general shorter compared to the Europeans, and that maybe the reason. But in that case Brazil and Argentina should not perform so well. I strongly suspect that there is some other reason.
I think it's very difficult to look at Asia as one continent because the differences between nations in mentalities, economic development, popularity of football, are really huge.
Due to the 2002 World Cup in Japan and South Korea, large investments in football began in these 2 Asian countries and already at the 2002 World Cup South Korea was fourth in the world, which was a miraculous and unexpected result.
African or North American national teams are still waiting for such an achievement.
South Korea and Japan are still strong teams, dangerous to any team in the world.
Does anyone else remember the first half of the match between Japan and Belgium at the last World Cup in Russia. Belgium, which later knocked Brazil out of the competition and finished in third place, just happily continued the competition.
Other Asian national teams do not invest so much in the development of football, or football is not their most important team sport, and therefore do not achieve such results in major competitions.