Best way is to destroy scams. Having scammy exchanges, scammy people running away, this is what make the trust to do not come. Little by little, by not funding them will make them disappear, and a trust will be contructed over the time.
You can't take all of them down. And even if you successfully do somehow, there will be new scam sites opening up. It's not that hard to make a website if you hire a web developer. And the cost of that is nothing compared to how much these scammers will make. I think what we should do is educate people about such scams. If they are aware of these scams and how they work, then people will know where not to invest to. Thus, these ponzi scams, no matter how many new gimmicks they come up with, will not have that much investors. Hence, they will find other ways to make money. Probably just another way to scam, but people only have to educate themselves once more.