So it's important to note that when we talk about the executive branch that the only elected officials who occupy this branch are the president and vice president. Everyone else is on the cabinet and is appointed by the president, himself.

Because these other members are not elected by the people of the US, there have to be strict guidelines on what they can and cannot do politically.

Fir instance, partisan activities. Let's say the US elects a liberal president from the democratic party. Though highly unlikely, the president could choose to appoint an alt-right Republican leaning independent to be the secretary of treasury. Since the US did not elect the secretary of treasury, it wouldn't be proper for him to use his position to engage in partisan activities, such as raising money for the republican party, or solicit any political contribution. Additionally, he should not use his position to aid in voters registration unless it is non-partisan. Meaning, he should not be campaigning specifically trying to get Republicans to vote.

The president and the vice president are able to do these things because they can only do them for either non-partisan benefit, or for the partisan benefit of their running party. This is not considered corrupt because the American people are generally aware of the political association of the president they elect.