Umair, this isn't only a problem affecting men. Lots of women (AND men) go to school, get good grades, are talented, bright, hard-working, help at home and in their community, do everything they're supposed to do. Yet the few good jobs go to children of people with connections and power... and wealth. Even if those children didn't study hard, aren't qualified, experienced, or innovative, nor good leaders, it doesn't matter. 50-100 years ago, it was more due to gender; now it's more about families, or dynasties, a great way to describe it. (Politics reinforces this, as so many Congress people have parents, wives, then children who are in elected office too.)
The first time I heard of nepotism privilege was from Dinesh d'Souza. He said that coming of age in the late 1990s and 21st century is like living in a "Casino Economy". A very few people attain huge wealth and success quickly, often right out of school, without working for it or being deserving (e.g. inventing something). It's like they win at the casino just because of the family they were born into. This was always true to some extent, but your graph (which is excellent by the way!) shows how something is really wrong with the US economy. Downward income (and wealth) mobility shouldn't have gotten worse for THREE generations in a row.