The season typically starts out with about a half dozen contenders, depending on definition and context.
After the first few weeks a name or two is added to the list while a name or two are subtracted.
Towards the end of the season, a mystery team emerges, one whose momentum in December cannot be ignored.
As the postseason begins, there are the true contenders and there are the "filler" teams that are there because, with 14 teams in the playoffs, somebody has to be there.
There is no series. You win or go home. Any team can lose a single game. Just because a good team is eliminated, it doesn't mean they weren't contenders. Some don't care to admit it, but there is an element of luck involved. The Cowboys and 49ers, for example, were on the bad side of luck last season when they lost key offensive players in the middle of a game.
The arguably best team wins the Super Bowl about 50% of the time, the other 50% fail to make it through the playoff gauntlet.
Thus far, the Cowboys are a contender, previous results count for nothing. These are not accumulative circumstances, every season has it's own story. The Cowboys were generally expected to be a good team and they have done nothing to discourage that perception.
The Jets were contenders. However, unless Zach Wilson goes through some miraculous transformation, they should lose some key games to start the season and they will be eliminated as contenders, perhaps not technically, but for all practical purposes.
If, on the other hand, the Cowboys lose to the Jets, suffer an upset to the Patriots, then lose to the 49ers, then they will be the ones eliminated as true contenders in the minds of most.
Today, the Cowboys are contenders.