If the exchanged volume is 10-20 times of the total coins, which indicates the scammers has existed
You mean "exited?" There is no way to know that especially in an anonymous coin.
Monero trades hundreds of BTC per day yet I still hold some of the exact coins I mined the first week. I did move them once into a holding account but that's it.
Just because some coins turn over many times does not mean that all the coins have turned over even once.