TBF to Amazon the remote work environment changed a ton since they made the deal. Whatever government made the deal probably should've had some language to re-negotiate but you can't plan for a pandemic to happen.
I never knew what the story was with crystal city until I just googled BRAC. A largish NAVSEA office is based there and it is super convenient to fly into Reagan and basically walk there…but it was always a ghost town.
It mostly happens because people die and their homes come to the market. It will happen in any city over time unless the economy completely bottoms out. It’s a natural cycle of life that is required for any area. If it doesn’t happen somewhere, the area is dying.