Already an economic juggernaut, they are undertaking the largest infrastructure project in human history. Linking three continents with road and rail is no mean feat. Incidentally it will also give them a massive advantage should war break out. China is looking to a future as the dominant economic and military power in the world.
TPP was a way to slow this growth. But America is choosing to become a second class power. We are always stronger when we engage the world. In a connected world there is no wisdom in trying to go it alone.

You think America's global leadership is bad just wait until you see China's.

"The Race for What's Left" by Michael Klare.