I've got a much simpler one: getting to the US from their (generally much poorer home country) was a brutal selection game for many people of those races, and they come from cultures that emphasize education as the primary means of getting ahead in life. The ones that made it are naturally going to be the most motivated, educated, wealthy, and/or otherwise lucky people, on average (there are always going to be exceptions). I'm frankly in awe of what the people whose stories I've heard have accomplished from where they started.

The children of those people would have two parents of above-average motivation and belief in education coaching and driving them from a young age.

Viewed in that light, of course they're going to do well in school and be overrepresented in higher education. That's been their explicit, overriding goal, and they've had very motivated coaches helping them along.

Of course these aren't universal things, but they're common enough to have caused a stereotype to form, no convoluted conspiracy of elites scheming to manipulate society necessary.