King Saul made David an enemy of Israel, and David refused to fight back. This is the story of how he got support to claim the throne.
Many soldiers joined him, even some who went possibly to spy on him ended up joining him. The story is told of the man who became commander of the elite ’30’, having a prophetic utterance, recognising God is on David’s side.
The structure of the narrative makes it clear he is a unifier: it goes through all the tribes, listing his support, starting with Benjamin, Saul’s tribe.
The momentum builds until he has a huge army, the people gather to him, and the is spontaneous feasting and joy, he’s that kind of guy in that kind of moment.
David followed God, and God’s plan unfolded around him.
I have a small sense of that at work, I get panicky if I try to think of the big picture, but I clearly know what would be the right thing to do moment to moment. David surrendered to God the big picture.