You’ll notice the messenger apps used around the world have a rather nationalistic slant to it. China uses WeChat (and blocks Kakao and LINE) because WeChat is developed by a Chinese company, Tencent, and the Chinese government wants to monitor all the messages on its platforms – WeChat complied hence it has a strong national interest to keep WeChat in use by mainland Chinese people.
Taiwanese and Japanese people use LINE – which is by Naver (actually a korean company who expanded to Japan) – LINE is dominant in Japan as it is made by Naver Japan and has a strong presence in Japan. Taiwanese has a strong historical connection to Japan and naturally they use the same chat software.
KakaoTalk is by Kakao Corp a Korean company and because of its domestic heritage is heavily advertised and very popular in Korea. Koreans do not use WeChat or LINE because among other reasons, national security (Chinese government spy on WeChat, Japanese government spy on LINE) and nationalistic reasons (Korean government spy on Kakao so it has national interests to push it to Koreans).
KakaoTalk is not as well known outside of Korea as WeChat and LINE and the reason for this is simply because WeChat has a lot more users (way more Chinese people) and LINE being from a bigger company has more resources to expand abroad. KakaoTalk has to compete with not only WeChat and LINE but also Facebook Messenger, WhatsApp and Viber abroad, and it just doesn’t have the resources to beat those companies.