Pressure can also make diamonds and I know a lot of people who have become incredibly driven and successful precisely because of what they went through, while others who have had it easier tended to coast through life.
I don't think it is possible to separate out all the individual parts that go into making someone driven and successful, especially not with only anecdotal data
I see privilege as both a head start and a multiplier to your individual effort. People who put in no effort will still end up nowhere unless they have an absolutely enormous amount of privilege that allows them to succeed on a head start alone.
Someone with little privileged who puts in a huge amount of effort can overtake someone with a high privilege who puts in a normal amount of effort.
