If a government has money to spend planning long term 5- 10- 20- 50- 100 years out🤺 on infrastructure in foreign nations is not a bad idea to build big with growing room.
If you believed it would be harder to build a large property in 5 or 10 years time build and hold is a good strategy.
If you are building a castle wall and mote you should think about what happens when yea olde grandechilder grow up or you need to hire and house lads to man the walls.
Or ..... someone has plans to move the embassy to a new location and sell off the existing property.....