Market cap rising 2 times doesn't mean that so much money has actually been poured into Bitcoin Cash overnight. It is a way, way lower than that. It is only a small fraction of all coins that get traded, therefore you don't need billions of dollars to raise the market cap that high. That's why this metric is misguiding. People think there are literally something like $30 billion dollars in the market but it is far from that in terms of real dollars.