A significant percentage of recruits from Florida, Texas, and California eliminate ND because of its distance, and, instead, look to the schools close by.
You're right - many of ND's best players from the past 30 years have come from far off places. And, really, that proves my point: unlike SC, Bama, and Miami, ND has to convince the country's best players - and their families - to spend 4 years at a place that's a 12-hour drive, or a 4-hour plane ride, away.
And while we cherry-picked some great players from Texas, S. Carolina, California, etc. in Holtz's years, we also had a huge chunk of talent, and really, each class's foundation, coming from relatively nearby, northern cities and states: from high schools in Chicago (Oliver Gibson, Pete Bercich, Bryant Young, Zorich), Michigan (Jerome Bettis, Randy Kinder), Ohio (Marc Edwards), Pennsylvania (Ray Zellars, Rocket, Ricky Watters, Powlus), Wisconsin (Flanigan), New Jersey (Irv Smith), and Indiana (Mirer, Derrick Mayes).
There just aren't as many good players in those states anymore. Populations have shifted. Participation is down. Some schools and programs have shuttered. Now, there are fewer and fewer Jaylon Smiths within a 6 hour drive of South Bend.