No, that's s almost exactly backwards. A key way Clinton locked out other traditional candidates was to secure an unusually large number of superdelegate commitments extremely early, needle other candidates would normally commit to the race.

> IRV can make the contest more fair than the previous voting system, but it can't make candidates run...

Yes, it can. Running in a Presidential primary (and the same is true of many other races) is an investment of time and resources people make—or avoid—in part because of the perceived prospects for success factors like a competitor having a substantial share of the total available vote sewed up before you decide, or a voting system that naturally narrows the field people will actively consider during the campaign do, very much, effect who decides to run.