I think lack of success of foreign apps in China comes down to a much simpler dynamic. Foreign apps are simply not launched concurrently in China and optimised for the Chinese market from the outset. The exception to this are mobile games titles which are generally overly optimised for the Chinese market if anything and generally fail to succeed outside of it.

This results in Chinese clones of said new foriegn app/service appearing very quickly and gaining dominance before said app can "expand" to China. By the time that happens, if it does, they have to compete with an established service that is language and culture native.

Essentially if you aren't launching in China day one and have a great understanding of the -very- competitive Chinese Internet platform economy you are screwed before you even start.