the STEM academic world in the Soviet Union was extremely meritocratic. largely shielded from outside influence and maybe the best talent pipeline anyone has ever invented to produce scientific expertise. Exception being biology as Lysenkoism at some point infected the field.

Corruption affected history or economics because it was ideologically relevant to authorities but math and physics proceeded on its own.

This is an oversimplification. Yes, there was corruption, but it was much less corrupt than the US system, especially today. The US system doesn't try to hide it either, everyone knows about legacy admissions and "school spirit"/donations.