I think the writing was on the wall when Notre Dame missed on both Walker/Westbrook. They had recruited phenomenally from 2009-2016, routinely landing really 1-2 top 20 players and several top 5 kids, but after striking out in 2017 and not landing any big names in 2018, they were left with a barren cupboard and no proven underclassmen ready to take on bigger roles after their 2019 class departed. None of the 2019-20 returnees were contributors prior to last season so it was essentially a brand new, inexperienced and much less talented and roster for Muffet and we saw how disastrous that was.
In her defense, the original 2019 graduating class was going to be just Arike and Mabrey, but Turner's ACL gave her an extra year, Shepard transferred in and famously became eligible a year earlier than expected, and Young declared early which meant all 5 starters were gone. The other 2016 recruit, Boley, had transferred out and Muffet was left with a roster of players who never played long or meaningful minutes. Im guessing Muffet originally anticipated that she'd have Shepard and Young on board for 2019-20, plus a more experienced Kaitlyn Gilbert and Jordan Nixon. Had that panned out as planned, it would've been a much different season for ND in 2019-20.
Worth noting, "go big or go home" classes that have 5 senior starters create massive voids that can incite growing pains the following season, or can even completely derail a program. We saw this with LSU in 2008, where they made 5 straight Final Fours from 2004-2008 but haven't been close to getting back there since. Tennessee also graduated 5 starters in 2008 which in conjunction with injuries led to Pat's worst season of all time in 2009, although they bounced back well in 2010 despite not being at the same level they were in 2005-2008. Oregon has avoided a bad season despite losing their 4 best starters from a year ago and has looked really solid this year despite having a brand new roster. They have a couple of impact returnees back though between Boley/Chavez.
Last year we saw ND get completely derailed,, and this year ND is still somewhat of a mess between injuries, covid, and transfers. There isn't a cohesive returning core to build the team around like there always was during Muffet's era. I think if they can stay healthy, they'll be much better in 2021-22 since they're young, talented, and have another good class coming in, but obviously that remains to be seen.