God used the Assyrians to put pressure on Judah to repent. But instead, they fortified Jerusalem's defenses. They armed themselves with weapons (v.8). Those who tried to flee were captured. Judah was helpless to save themselves. The LORD called to them to repent and turn to Him. Instead of mourning and repenting, they feasted.
Shebna, evidently was one who could have been in a position to negotiate with the Assyrians. However, it seems he wanted to use this opportunity to make a lasting name for himself. Therefore, God rejected him as an unfaithful "steward" and replaced him with Eliakim. Eliakim served as a father figure to Judah, with the full royal authority that God place upon him. In verse 14, he had God-given power to make things happen on behalf of his people. But as secure as Eliakim's leadership was even it would one day come to an end.
At the heart of the problem was their unbelief that God could deliver them and that He wanted to deliver them. That sin of unbelief "will not be atoned for..." (v.14).
The writer of Hebrews stated, "Without faith it is impossible to please him." (Hebrews 11:6) When facing impossible situations, we first and foremost gladly cast our full dependence upon the God of the impossible. He alone can forgive sin. He alone can deliver us.
"Faith, mighty faith, the promise sees and looks to God alone;
Laughs at impossibilities, and cries it shall be done." -Charles Wesley