Recruiting outlets like on3, rivals, 247, etc do not have 1000 recruiting reporters doing standardized analytics to rate high school kids. They do have some and they review available film, but in most cases they take into account the opinion of successful recruiting teams. Alabama, Georgia, LSU, OREGON, osu ETC... these teams have huge scouting and recruiting teams that have proven successful at taking recruits and successfully getting them to the NFL. The shots they take on lower ranked guys gives confidence to those services to increase their ratings sight unseen, because of faith in those institutions.
Notre Dame doesn't. In fact many of the five stars Notre Dame has gotten outside of ol, have under performed or transferred...dayne crist, Johnson, Bryant, wimbush, etc.... Many 2-3 star guys never even see the field or if they do they stand out as slow or out of place. That reflects on how the coaches find and develop talent and the level of research done by that staff. What that means is that recruits that commit to Notre Dame don't get that bump, moreover if they commit early they will drop in the ratings without doing anything. It's because they are getting passed up by other 2-3-4 star guys that are committing or even being offered by programs held in higher esteem at identifying talent.
It's just one reason that ratings mean nothing.