Why do most American billionaires come from top unis but not the UK?

I'm just curious as to what people think about this. Go on a list of richest Americans and you will notice the top unis are very, very heavily overrepresented. Go on a list for the UK and it couldn't be more different, most people went to university but there is a huge range in selectiveness with many not going at all.

Part of it is probably because you can pay your way into a top uni in the US (43% of Ivy League entrants were legacies) and are a lot more exclusive due to the insanely high costs - so people from rich families are more likely to go there, and then get rich (Bill Gates was very rich, Jeff Bezos got 300k for Amazon, etc.)
In the UK, while top unis are classist, the fees are obviously the exact same - so while there is a big influence of your socioeconomic background, it's much less about being able to afford it as your academic ability. Obviously, if you are rich you are more likely to get in, but the amount it is weighted against disadvantaged students is less than the US. Also, in the US admissions system, extracurriculars play a huge role, and you'll often see kids paying thousands of dollars for these elite programs such as summer schools or research programs to boost their applications - but in the UK the top unis don't care about that - it's about your passion for the subject.

Hmmmm ok I think a lot of this makes sense, especially the extra curricular stuff.
I disagree with the fees, at least nowadays the Ivy League are generally free or near free for poor students. Also I think Jeff Bezos upbringing was fairly awful. It certainly sounds like it on wiki, 17yo mum, 19yo dad, alcohol problems, dad left when very young. I gather that his adoptive dad was probably much better but this sounds much worse than the average American upbringing. Gates and Zuck were definitely privileged though.

Really? It seems he had a pretty stable, middle class upbringing, albeit he was adopted. I wouldn't say his upbringing was 'awful' - the alcohol was with his dad, and Jeff's mum divorced him at 17 months old - he wasn't exposed to it. He graduated valedictorian, and was able to pursue his scientific interests during his childhood - I don't know where you've got that his upbringing was awful from? Then he obviously received 225,000 dollars for Amazon.
Zuck, Gates and the rest were all very privileged - I agree with you on that

Teen parents, father with an alcohol issue who worked at Walmart, divorced by 2, his bio father didn't have a clue who he was until a few years before his death. This is pretty much the definition of unstable lol. I suspect his adoptive father became successful later in life and that's where he received the money from but Bezos was already extremely successful before he received the money. I think he is one of the rare examples where someone is just exceptional.

He wasn't. At the time he had just quite a corporate job and it was literally right at the beginning of Amazon. Sure, he had a well paid job in hedge funds, but to say he was 'extremely successful' is false.
How does that constitute unstable? His father wasn't in his life, that is not the 'definition of unstable' and using examples like how he had an alcohol issue or working at walmart isn't really fair because he had no influence on Bezos' life. With regards to his adoptive father, he was an engineer at Exxon for decades and earned a good salary living in the suburbs - he wasn't successful later in life.

Jane Street is ridiculously selective.
It just sounds terrible overall even if it was better later. I don't know if I'd have been able to go through all of that and be successful and I was on free school meals.