The surrounding nations presumably don’t like the regional power shift of Jerusalem becoming viable again. Their plot to stop it first involves offering to join the efforts, to hopefully make it lose its racial flavor. Then they run interference, bribing officials to frustrate and slow down progress. Finally they write directly to the king.
It is actually not hard to sympathise with the opposition. Their assessment that a strong Jerusalem would be bad for them could be entirely fair. Their letter to the king is effective because it’s not really slanderous, it tells the new king to check out the history of Jerusalem for himself, and he finds a history of trouble and shuts down the work.
The only thing that stops it being an entirely predictable and reasonable power struggle is that it is god’s plan that Jerusalem should be rebuilt. And god is love. It’s god’s long term plan of love for the world that they have inadvertently stumbled upon and blocked.
I think this is a good passage to remember when we find opposition in the world to get confidence to carry on. As the blues brothers said, we’re on a mission from God. Christians today get a seige mentality, and think of opposition as the forces of evil to be destroyed. But they are only behaving as we should expect. Beating them is not the mission directly, our response should be faith based and between us and God. A refocusing on our mission. Like how David, in times of crisis, would go into the presence of God and be restored.