Saul is the doubting mind, the ruler who cannot hold to what he was told and so cannot keep the throne. The kingdom leaves him because a hesitant mind builds nothing that lasts. What replaces him is no sturdier version of the same ruler. His successor is David, and David is the whole human race gathered into one perfected being, the eternal Son of the I AM.
Here stands the man after God's own heart. All human experience finally resolves into him, and in the end he rises within a person and calls that person Father. The doubting mind steps aside for the Son who contains everyone. What governs at last is the one being every life was always becoming, awake within and naming you as his source. Effort never wins that throne. The Son does.