But Christ clearly rejected the earthly kingdom at that time, and did not take the throne of David, which is a physical manifestation, not a spiritual one. You are suggesting without proof that the throne of David is internal and spiritual, and not an actual kingdom. That's not how Christ viewed it. He did not correct the disciples's view that there was a physical kingdom coming. And I'm sure David would have been surprised to learn that he did not have a physical throne.
Acts 1:6 "When they therefore were come together, they asked of him, saying, Lord, wilt thou at this time restore again the kingdom to Israel? 7 And he said unto them, It is not for you to know the times or the seasons, which the Father hath put in his own power."