Universities are effectively ultra-anchors. You have large numbers of students from mostly middle class backgrounds, many of whom have free time and disposable income. (Or at least they're not worried about their loans yet.)

And then you have the academics. Tenured profs are relatively well paid. Adjuncts/assistants not so much, but they still like nice things.

The UK's public school towns (Marlborough, Harrow, Winchester...) often have a prosperous independent store economy on a smaller scale, for the same reasons.

Clusters work well in these towns.

If you try them elsewhere, like one of the UK's many run-down towns, they're more likely to fail because the prosperity just isn't there.