There was literally nothing except an obscure village or two when construction started in 2002, and the official population figure of 900,000 is widely regarded as preposterous. (The video I linked to above guesses 100k tops.)
I took a look at the satellite images. It's a bit hard for me to gauge what the entire area that is supposed to comprise 900k people is, but the official numbers for Pyinmana (inside the capital district but not the capital itself) is about ~100-200k, and Pyinmana is visibly more dense than the city of Naypyidaw itself.
In contrast to Brasilia (which is perhaps the most well-known recent-ish create-a-new-capital-from-scratch initiative), it is far less dense and less occupied. Contrasting to most of the other newer similarly-situated capitals, Naypyidaw is clearly pretty poorly populated and some of its infrastructure is laughably oversized compared to what use it would actually get (Why do you need that road with 10 lanes in each direction? It goes from nowhere to nowhere...).
Putrajaya in Malaysia (est 2001) is an interesting comparison. It's also overly ambitious and oversized, but it's not quite as nuts (the empty highways are 3-4 lanes, not 10), it has a comparatively far more sane location (between Kuala Lumpur and its main airport), and its actual population is around 90,000.
And of course Astana - or now called Nur-Sultan to honour the Kazakh president. Also has the similar highways that can just be used for airplanes if needed. The city was a ghost town in the weekends when I visited 6 years ago, because all government personnel takes the night train to Almaty in the weekends.
Interestingly, Brasilia was modeled after the build-up of Washington DC - a remote capital that would not allow undue influence from any one existing US State.
