But why we should trust someone that he has the gold in the vault and the token is really backed up with real gold?
Because Chain Security have reviewed the projects design and architecture for compliance with best of their practices and assure the project is good to go in terms of security and to deliver the highest assurance guarantees. Look at Tether, they promised that they back every USDT 1:1 to USD. But now? They changed rules.. 
Firstly, I want you to know that you can not manage people or an investment which glaring shows that the future is actually not promising or else you'll be badly affected. We both know that the reason why cryptocurrency was created was because of inflation/economic meltdown and you see a project which calm to be stable while their project was backed with the same national currency which was affected by inflation and you totally trust? The digital gold token team is here to the crypto sphere and the world a better place.