Because people can be both honest and dishonest about different things or at different times. No one is perfectly honest and even the worst person is probably honest some of the time.

> ...considering his status as the world's richest man makes me think he should be held to a much higher standard

This makes sense in some ways and absolutely none at all in other ways. The richest man should be judged harshly for displaying greed, for example, but not for making mistakes that money doesn't help prevent.