Short answers, pulled from the story.
The 1921 NFL Championship controversy, known as the Staley Swindle, was a dispute over whether the Buffalo All-Americans or the Chicago Staleys deserved the 1921 APFA title. Buffalo had the best record in the league, but after losing what their owner Frank McNeil called an exhibition game to Chicago on the 4th of December 1921, the league awarded the championship to Chicago using a newly created tiebreaker.
The phrase "Staley Swindle" was coined by researcher Jeffrey J. Miller to describe what Buffalo fans and historians view as an injustice. Miller argued that the All-Americans were wronged when the league counted a game that Buffalo owner Frank McNeil had publicly described as a post-season exhibition with no bearing on the standings.
The central figures were Frank McNeil, owner of the Buffalo All-Americans, and George Halas, owner of the Chicago Staleys. McNeil maintained the December games were exhibitions; Halas argued all games had to count and persuaded league owners to adopt a tiebreaker favoring Chicago.
The executive committee created the league's first championship tiebreaker, ruling that in a two-game head-to-head series, the second matchup counted more than the first. Chicago had won the December 4 rematch 10-7, so the tiebreaker handed them the title. The NFL abolished this rule in 1933.
Buffalo never returned to the success they achieved between 1918 and 1921. The franchise barely stayed above a .500 winning percentage for three seasons after the controversy, then fell to the bottom of the standings for most of the rest of the decade, suspending operations in 1927 and folding in 1929.
The controversy pushed the APFA to set a fixed end date for the regular season to prevent teams from scheduling extra games after rivals had finished playing. Later, when Chicago and the Portsmouth Spartans tied for first with no applicable tiebreaker, the league was forced to schedule a playoff game, which became the forerunner of the permanent NFL Championship Game.