I do not know if luna could be rebuilt or not but it will be one of the biggest disasters in crypto history and shows us sometimes how vulnerable Defi could be. May be team could save luna by leaving UST. If they really could repeg UST then it already lose its trust and no one will hold that again. So the team's best bet was to save luna which was not their priority.
 
I have also heard that Do Kown shorted his luna after selling his reserve BTC in a loss. This could be rumors but if this is true then he knew what is going to happen with luna but he didn't warn his community not to buy luna. His mountain-high ego and pride make enemies around him.