Couple things, Olen’s bad years are when UCSD was transitioning to D1, hard to recruit when you can’t go to the tournament.
Hartman has been an assistant but really worked his way up the assistant ranks, he was at places like Rice, La-laf, Columbia for 20 years. The staff at Columbia had Kyle Smith, Todd Golden and Hartman. It wasn’t until the success there that he was able to move to larger D1 jobs. So it appears he was happy to work his way up as an assistant and not just jump to any HC job. There could be many reasons for that, assistant jobs are usually more stable (if you find a good coach), maybe he felt he had more to learn, maybe he felt liked he could connect with kids more as an assistant. Just being an assistant should not disqualify but sure previous head coaching experience is better for other candidates.
With the success of Calhoun and other former D2 coaches across the country, I think Olen might be the better choice between these two. Probably more solid and less downside risk. However, I think Hartman might have the higher upside but for sure much riskier.