Idon't really get this can someone explain

Well, the credibility gap caused a huge amount of distrust from the people toward the government due to the "coverups" the gov. gave about the Vietnam war. It is difficult to try to run a country when the country doesn't trust its leader. If you are questioning the diagram, you just need to draw the diagram and write the causes leading to the fall in support for the Vietnam War effort. Hope I helped!

The answer is challenging and taxing because arduous means when something is hard and tiring and the excerpt provides clear detail why that's the answer