Best way to have social capital is an introduction into a space where money and power exist. Many spaces no matter what you do you will never be able to get in without an intro, and they have extremely few opportunities. Being college buddies with a member of an upper class is one of the only times they will ever socially mix. It is indeed like royalty in every way.

Being at Harvard gets you a lot relative to the population, being around the right clubs at Harvard gives you a lot relative to that. There is meritocracy within the range but nepotism can easily put people in the room. Work at a startup or two run by families of billionaires, and watch their career trajectory, and you will not have any doubt.