I don’t think any of the Mary’s on the first tour was a UMich grad, although Steffanie Leigh was a recent CMU grad when she landed the role. Maddy Trumble on the second national tour was a UMich grad. And, of course, the original Broadway and first national tour Mary, Ashley Brown, went to CCM. Again, as @MomCares says, for what it’s worth. Leads and ensembles in all kinds of productions come from all kinds of schools. Or no school at all, like Jonathan Groff. There are plenty of paths to success, not to mention all sorts of different definitions of successful.
And lest you all think I’m a complete Poppins-o-phile or something, I only know because my daughter was on the first national tour. She performed almost her whole stint save the last week with Steffi, who still serves as a role model for her.