Were they additional airports or renovations of older ones?
Singapore and Hong Kong don’t have much land area so I would think they had an airport available more than 20 years ago.
Brand spanking new.
The one in HK was the largest reclamation project in the world when it was built. It sits on an artificial island as big as Kowloon. It is a huge (300 gates) but somewhat sterile looking airport.
The Singapore airport opened about 5 years ago and has basically an amusement park in side. The airport is a tourist attraction.
The Istanbul airport opened in 2021 and looks like a shopping mall.
All of them are huge easy to use and attractive.