You might be misinterpreting. His nomenclature is misleading, but he doesn't mean "2x", he means "2X", where X is the number of companies. That is, you give 1 million € to 10 companies, and the one winner makes you 20 million € (20 times what you invested).

He's saying you are guaranteed to double your money in 5 years, which for most investments isn't easy. Or maybe you understand this, and mean that a VC firm needs to target even better returns than this to stay cover their costs and stay in business? Possible.

I don’t know if every VC had an unicorn at least once in their portfolio, but for early stage investments to be a good idea they just need to beat consistently any other investment opportunities.