Hi Magic, let me try...
The rankings that you're inquiring about are for THIS year's team. Last year's team ended the season ranked # 1, and recognized as the National Champion by all of WCBB.
This year's team has a 4 game win streak, not 79. THIS year's team has not won anything other than those 4 games. Notre Dame is ranked #1 by whoever the author of that ranking is because whoever did the ranking feels that Notre Dame is a better team that UConn at this time. If UConn beats Note Dame next week, UConn will move up 1 spot , and be recognized as the #1 team nationally.
Different people (AP, coach's poll, ESPN, USA Today, etc) produce their own rankings based on their judgement and the results of their "eye tests". UConn is the defending national champion.
That does not mean they must be (or deserved to be) ranked #1. They will retain that destinction until a new winner is crowned at this year's final four championship game (Dallas Texas) in April 2017.
Rankings at this time of year really don't mean anything to the coaches, only the fans. For those of us who are of that persuasion, those rankings give us bragging rights, nothing else.
Rankings are only important at the end of the season, when they are used to determine invitations and seedings for the NCAA tournament. Right now, having a high or low ranking, is not going to make a team play any better, or any worse. I hope this helps.