You right. Market capitalisation is not like "active is priced $2 trillon MC so there is $2 trillon is injected and waiting somewere". It's a slice of current demand and supply. If someone buys 10 BTC for 100k each and that's all for a day, than the price of BTC that day is set to 100k and it's MC goes to 2 trillion. Even if it's just one million (10x100k) worth is actually traded.