People trust "authority" because they don't have time, resources, training to build the body of knowledge themselves. It is not feasable neither desirable for everyone to know about everything. Societies build chain of trust and that's why institutions are important. Think of authority as a function call in a big framework which provides an answer with reasoning for that answer. In my previous function calls, the authority provided answers properly. If I get a wrong answer, there is a "bug" somewhere in the system.