The PRC and Russian Federation don't financially dominate Africa. For the PRC, it's because they don't have a domination of their econlmy by private financial capital, they have a socialist market economy. The PRC stands to gain more from mutual benefit, especially since developing others improves trade circulation and provides more customers for goods they produce. Even ignoring ideological reasons like being Marxist-Leninists, they lack the economic compulsion.

For Russia, it's because they outright lack the financial capital to participate. Russia, for all of its productive capacity, fell dramatically from their heights as the Soviet Union. Russia needs to offer more favorable trades, as they cannot rely on the sheer overwhelming financial power the west has. As a capitalist country, it has every reason to want to be imperialist, but it can't, and as such it is forced to strategically align itself with socialist countries and against western imperialism. Further, KPRF membership is skyrocketing, meaning a return to socialism is legitimately increasing.