Why is there a Bye Week?

I hear a lot about bye/buy/by week in football chatter. So today I asked the coach at our breakfast table. And he explained it, but I wanted to know the origin, not the meaning. I've seen it spelled three ways.

This is what Why Do We Say Teams Get a 'Bye'? | Merriam-Webster site says:
"In sports, bye refers to a team automatically advancing to the next round of tournament play without competing and bye week refers to a scheduled off week for a given team. The term is not related to goodbye but is instead believed to be an alteration of by, as in the team is "standing by" to play later, or "bypassed" while other teams play. One early sport to feature a bye is coursing; the b-y-e spelling is likely influenced by an existing term from cricket in which a wicket-keeper misses a ball."

By vs. Bye: What's the Difference?: Grammarly says:
"The term bye is commonly used in informal conversations as a short way to say goodbye. Additionally, it has a specific application in sports, referring to a situation where a player or team advances to the next round of a competition without having to play."

So "advancing without playing" (which still doesn't make sense to me) seems to be the meaning of "bye" in tournaments, and it's not just football.

Where I live, I hear more sports talk in a week than I used to hear in a year,