The thing about communism, totalitarianism or whatever variation these people choose, is that it doesn't matter if it's failed every single time to them. It's the perfect system for wealthy, power hungry megalomaniacs to increase or at least maintain their status. Any kind of democracy brings with it the opportunity for them to be removed from their perch.
Spreading communism, failed as it may be, is the route to increased power, wealth and keeping it all for themselves. It's ok that it's a failed system because even if the people suffer, the leaders get to live large.
If China could facilitate the fall of America there is nobody left who could stop them. The combination of China, Russia alone could easily accomplish the world domination envisioned by every nut job from Hitler to Xi Jinping.