Manaus 44.000 people - It's in the middle of the amazon forest. There are places in the amazon that you need to get a boat to get there. If you get the public of all the 102 games in the state's local championship (29.180 people) you won't fill the stadium ONCE. They only have one team in the last division of brazilian championship and that's because every state has at least 1 spot. So they DO NOT have any professional soccer there and people in Manaus don't care about it. They got picked by political decisions ($$)

Cuiaba 43.600 people - Soccer there is amauteur. They have two teams in the third division (promoted last year) but it had an avarage of 1.000 people per game. They got picked by political decisions ($$), their governor is the biggest devastator of amazon and cerrado forest. He also made billions and a political carreer with that. Cuiaba was picked to be the city to represent Cerrado environment (ironic). Cuiaba city is also poor and isolated from the rest of the country.

Natal 45.000 people - They have 2 teams in Second division but they have no tradition in soccer. The city is very VERY poor, almost all projects of infrastructure got cancelled by lack of money or time and the stadium is in danger too. They got picked by political decisions ($$)

Recife 46.000 - State with very strong tradition in soccer and all 3 big teams in recife brings over 10-20k people every game. BUT none of the 3 teams will use the new stadium. Which isn't even in Recife, it's in a city near it. They all have their stadiums and they don't want to use the new one!

Brasilia 71.400 people - No soccer tradition. They have ONLY one team in the third division and it had an avarage of 800 people per game this year. They almost got relegated to the fourth and last division. Soccer there it's a joke, NO ONE IN BRASILIA supports ANY local team. They all support teams of Rio de Janeiro and São Paulo (mainly because 90% of people in Brasilia lived on those places when the city was built and brought to their families their culture and teams). It got picked because is the capital of Brazil.

Cities left out because of politics:

Goiânia

VERY strong soccer tradition. City was elected highest quality of life in Brazil last year, it's beautiful and in the center of the country near every other host city. It's also the greener city in south america. Huge stadium and a great project to reform it (Serra Dourada). It has money and should have been one of the first cities selected. BUT The governor was an enemy of the president and got left out because it's close to brasilia and cuiaba. Brasilia is the capital and cuiaba was picked for political ($$) reasons.

Belém

Very strong soccer tradition. These folks bring over 20k people every game of the 2 biggest teams. People in Belem LOVES soccer and are sick about it. It's also in the amazon forest but got left out because manaus was chosen for political ($$) reasons.

Florianópolis
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Very strong soccer tradition. They have 4 teams in the first 2 divisions and the city is beautiful. Very strong touristic place with amazing beaches and hotel infraestructure. I guess they picked Natal over florianopolis for political reasons.