The cities sure, but if you take Erie, Niagara, Monroe, and Onandaga Counties it's more like 2.3 million. If you add in reasonable counties in between like Orleans, Wyoming, Genesee, Cattaraugus, Chautauqua, and Livingston you add another 360,000. There are plenty more people in Central NY beyond that that I didnt count.
Then go ahead and remember you have another 100k people directly over the border in Fort Erie and Niagara Falls and a big swath of people reaching up to Toronto, many of which would be interested in watching a winning football team.
You also have tons of ex-pats who come back to town just for that. I've been one of those lots of time when the team was crap. It's a lot more motivating to drop the coin now that they are good.