The difference between centralized trust and decentralized trust is you can actually audit and reason about the system. In centralized trust you are typically hoping that human actors obey rules both written and unwritten. In decentralized trust the system is solely responsible and the code of the system is the exact rules it will follow. The tricky part of decentralized systems of course is have their designs been done flawlessly, so there are no vulnerabilities. (A very hard thing to do) In practice, perhaps decentralized systems do not have to be perfect, but just better than the centralized alternatives.
