Because Moshe was so humble, therefore, he was G-d's most trusted servant. Humility is knowing what makes each of us unique and special and developing those talents in the service of G-d. Servitude is accepting that our true worth is only in relation to how we use those talents to serve G-d. Therefore, Moshe is the most trusted servant of G-d because he was the most humble of all men. Moshe's understanding of his own unique talents and his acceptance that his sole value and justification as an individual was in proportion to the degree of his service to G-d, earned him his accolades as the most humble and the most trusted of all men.
Talent comes with a price.
Bright and talented people often struggle with issues of ego and self-worth. On the one hand they are acutely aware of their abilities. On the other hand, it is difficult for them to accept direction as how to best utilize those abilities. On the one hand, they trust their own intelligence in formulating their own opinions and decisions, and present their plans with a degree of confidence and bravado. On the other hand, they are just as fearful as anyone else of failure and rejection, but far less prepared to deal with either.