Why couldn't China just do that and support revolution elsewhere?

I definitely agree with this, but given the modern history of China and its local history (1980+) theres a lot of risk in losing these fights supporting revolution, and it crystalizes the international bourgeoisie against you. Especially like the Soviet war in Afghanistan, you stick your neck out for not a whole lot of gain (underdeveloped trading nations with shaky institutions) that the safer option is to just focus inwards, to not allow your population hear the siren song of liberalism, and then to work with and develop these countries, working with their institutions to maybe create a proletariat capable of wielding power that is hopefully ideologically allied to you a la the Belt and Road Initiative.

I wont claim that China could see Western Powers devolving in the wake of the Soviet collapse but the West really didnt waste much time stretching their legs and continuing their wars of aggression, Gulf War, bombing Yugoslavia, and ultimately taking one too many risks that like in the USA left them to focused on foreign adventurism than keeping the lights on at home. America after the collapse also kept a list of enemies especially going into the 21st century that didnt have china on it. It had Saddam, Kim Jong-il and Khomeini. And that list got smaller and smaller and China only now is on that list.

We also cant really say that the Chinese method has worked yet. We're still a while out of the total collapse of Western Hegemony, and while China is ascendant, theres still doubt in my mind that BRICS could hold up the world economy in place of America. The world seems likely to change very fast in a very chaotic way, and China's stalwart development seems like the only thing that could change without being destroyed by it.