Asia literally covers a lot of territory, both large and small (China, Japan, the Koreas, Hong Kong, Thailand, Philippines, Singapore, etc.) And, I am not quite sure all Asian marriages do last longer than the Western ones. Asia also includes a lot of different religions such as Hinduism, Buddhism, Taoism, and Shinto just to name the more popular ones. But, let’s assume it is true that Asian marriages do last longer.
The answer may be that country-specific laws and religions, along with traditions and cultural beliefs are more focused on keeping marriages together. For example, some Asian countries require mandatory cooling off periods involving the families of unhappy couples be undertaken before allowing divorce to proceed.