Replacing Shebna, Eliakim will be given the steward’s official garments along with the key of the house of David.

And I will clothe him with your robe, and your sash I shall firmly bind about him, and your dominion I shall give into his hand; and he must become a father to the inhabitant of Jerusalem and to the house of Judah.

Thus, the office of steward is important, and much is expected of whoever serves in it. (Luke 12:48) Shebna may be capable, but because he is unfaithful, Jehovah will replace him.