The king’s heart is in the hand of the Lord like channels of water; he turns it wherever he wants. (21:1)
I think this concept is giving a lot of people hope right now in the middle of our current government situation. Part of God’s sovereignty is that even human government (established by God in Genesis 9:5-6) is still ultimately subject to him – even those that refuse to acknowledge him.
The NET Bible study note puts this very succinctly:
The verse uses a single sentence to state that all wisdom, understanding, and advice must be in conformity to the will of God to be successful. It states it negatively – these things cannot be in defiance of God (e.g., Job 5:12-13; Isaiah 40:13-14).