Read an article here about the causes and history of Japan's ban on meat. At the end of the article it mentions that Japan absorbed "meat-based dishes from Korea, China, and the West.".
Was Korean agriculture so much richer that it could support the consumption of meat? Or was there some difference in the schools of Buddhism? Japan's population was almost double that of Koreas by the middle of the 19th century though maybe density of arable land vs total arable land created more food, but not enough space for livestock?
*The title says "Why did Japan ban the consumption of meat, but not Korea or Japan?"
It should say "Why did Japan ban the consumption of meat, but not Korea or China?"
The bans on meat eating (or perhaps more accurately, the restrictions on meat eating, especially beef) were for two main reasons: (a) to protect cattle for use for traction, and horses for riding, and (b) to avoid killing animals, to act according to Buddhist principles. At least, these were the reasons stated by the lawmakers.
The laws were not absolute. There was generally a loophole that meat consumption, including beef-eating, was allowed for medicinal purposes. Total bans were rare, and did not always cover wild game (and not all wild game when some was protected), and did not always cover all domestic animals.
However, even when meat-eating was allowed, there were social taboos against eating meat, especially beef. This at least reduced ostentatious meat-eating.
For a past answer on restrictions on meat-eating and beef-eating in Japan, see https://www.reddit.com/r/AskHistorians/comments/asz87q/no_beef_eating_in_japan/
There were similar bans/restrictions on meat-eating and beef-eating in Korea, for the same reasons as in Japan: to preserve cattle for traction, and Buddhist non-killing. The bans in Korea and Japan appear to have started at about the same time, during the 6th century AD; Buddhism arrived in Japan shortly after it arrived in Korea. As in Japan, game was often not protected, and the meat of domestic animals, including beef, could be eaten for medicinal purposes. While beef could be - and was - eaten, whether as medicine or otherwise, there were social taboos which reduced consumption.
After the Mongol invasions of Korea, and the submission of Korea to Mongol rule, beef-eating enjoyed a renaissance, and became more acceptable as an upper class food, due to Mongol preferences for beef, mutton, and horse over pork (due to the lack of pig herding on the steppe). However, this had little impact on the food of the majority. Most Koreans ate very little meat, with many farmers eating meat (not including seafood) on only a few occasions during the year (and the meat that was eaten was often considered to be a fortifying medicinal food).
Up to about 150 years ago, Korean and Japanese food were very similar. A typical meal in either country consisted of grain, soup, and some side dishes. The grain was rarely all rice, let alone white rice - much more common was rice mixed with barley or millet, or even a mix of grains without rice. The soup and side dishes would rarely have meat, even for reasonably well-off people, and extremely rarely for poor farmers. I discussed Japanese food in https://www.reddit.com/r/AskHistorians/comments/81d8gf/what_was_japanese_cuisine_like_during_sengoku/ and Korean food at the time was very similar. Modern Korean meat eating only has weak traditional roots. It does owe something to beef-eating in royal cuisine, which as already noted, was partly due to Mongol influence. However, Japanese cuisine meatified long before Korean cuisine, and the colonial period, when Japan ruled Korea, helped drive Korean cuisine towards meat-eating.
Poverty minimised meat-eating in Korea, even when the social taboos against meat-eating were largely gone. At late as 1970, when the Korean economy was recovering from the war, Korean meat consumption was only 5kg per person per year, and was significantly lower just 10 years earlier. Today, Korean meat consumption is about 70kg per person per year, similar to that of Japan.
Japan cuisine did absorb foreign meat-dish recipes. The West was a major source, with Western meat dishes such as hamburger (hambāgu in Japanese, and consisting of a patty served with rice rather than in a bun), curry (adopted from the British), and breaded pork cutlets (tonkatsu) being popular both in home-cooking and eating out.