Can't make a single assumption on what if scenarios

Your first question assumes that the only condition that would have changed is Clark came to Notre Dame. I believe significant other changes could have happened that make it difficult to answer your question.

1. Would Muffet have retired when she did?
I think there's a good chance she would have stayed for CC's for years - perhaps like Auriemma and Bueckers at UCONN.

2. Would Clark have developed the same way at ND?
She may have become the same quality player (and perhaps better), but she would have been the top player within the system (i.e. nowhere near the scorer she was at Iowa).

3. Would the same players have enrolled at ND if she was here?
My guess, within zero knowledge, is that I question whether Olivia and Sonia would choose ND. It's also hard to judge recruiting if Muffet was still the coach versus Niele. But then, I'm not sure Iowa's failure to recruit elite players alongside Clark means the same would have occurred at ND.

3.