Why has transparency become so important in the post-trust era?

This is immensely important as it helps alleviate the fears of the public, which is fearful of unlawful and unethical workings of the government and the big corporations. In this post-truth world where individual emotions and beliefs influence the public opinion more than the clear facts this is really important, because when the things are transparent it is much harder to manipulate the public and play with the facts.