How Does Berkshire's Return Come From?

There's this debate of like, okay, where does Berkshire's return come from? Is it the leverage? Is this the stock picking? Is it buying things? Is it like an accident of history? Because multiples were so like valuations were so cheap. And I was thinking like, are there more examples of things like blue chip stamps where he found something that was just a very shrewd purchase and very undervalued?"