China cannot become powerful enough to challenge america alone, they need an ally, especially a powerful one like Russia.

That's tunnel vision. In reality Africa is urbanizing so fast it exceeds even the rate of what China did. The amount of resources in the ground of Africa is so rich that the nations on this continent should be the richest in the world. So you can say that if someone rule over the whole african continent can basically fight anyone.

China works on this since a long time, even building what many people call "colonies". Russia works on it too and recently chased the frenchs from Mali, fought in Syria, befriends dictatorships like Iran, and generally push a lot their propaganda in Africa to turn the african nations to them.

This current war is also a way to get some influence in Africa. You don't see it and will never admit it as you buy the russian narrative, but there's a reason why Russia is the first exporter of wheat despite having such a poor soil to grow wheat ; because of the climate most of the "wheat band" of Russia can only harvest wheat once and because it's so inefficient to grow food there, it's also quite poorly industrialized. But as a vital product, wheat allows to "buy" influence in the drier parts of Africa. As Ukraine was turning to the EU, and could get influence for the EU, Russia decided to grab the southern part of Ukraine, where the trade of wheat and other goods happens. That's why Russia tried since the beginning to take Odessa, even though they should have taken Kharkhiv, Sumy and other cities near their border if we believe their "push NATO away" narrative. Meanwhile, when they lost the battle of Kyiv it was just "-shrug- we didn't care anyway". But a small untenable thing like Snake Island, however, they held it an unreasonnable amount of time.