It's growth is mainly driven by migration from other states by people attracted by the high quality of life (highest in the country) and high-paying government jobs.

However, the designed neighborhoods are currently noble areas where only rich people can afford renting/buying apartments. Poor families are forced to live far from the city center (think 2-3 hours by bus) in dangerous places controlled by organized crime. For instance, Sol Nascente will most likely become the largest favela in Brazil (even larger than the ones in Rio since it can grow without being limited by surrounding mountains).

[1] https://epoca.globo.com/sol-nascente-favela-de-brasilia-que-... (Portuguese only)