You really think there are only 15-20 jobs better than MN? Watch stadium put up a great series where coaches ranked jobs. MN got 10th out 14 in the big ten alone. This is my point exactly, I think MN can be turned into a better job, but it's not as enviable as many think it is. I think if they ranked the top jobs in the country, MN would not be in the top 50 right now. Top 75, yes easily. Those rankings are fluid of course, but there are some things that just are not thought of highly by others.
https://watchstadium.com/news/big-ten-basketball-coaches-rank-the-best-jobs-in-the-conference-10-11-2018/
I think you have to differentiate between jobs that are slightly better than Minnesota, and jobs that are so much better that you leave behind the success and job security you have hypothetically earned at Minnesota to possibly do a rebuild at another school. If a coach, say, went to the tournament 3 straight years here and gets a Sweet Sixteen appearance or two, would you be worried that he'd leave for a job like NC State or Oklahoma or Oregon or something? Those are probably better jobs, but maybe not so much better that you'd willingly uproot your family and leave Minnesota for them.
As someone else noted, Big Ten basketball coaches do not frequently leave their jobs without retiring or getting fired. I think Ed DeChellis leaving Penn State for Navy was the last time it happened, and even that one might have been more of a "get out ahead of the firing squad" type of departure. I'm pretty sure Bill Self leaving Illinois for Kansas was the last time a coach left the Big Ten for a definite upgrade.
Money is an interesting angle though. I don't pay much attention to how money different schools from different conferences bring in from TV contracts, but I thought I heard the reason Purdue was able to pay Jeff Brohm 6 million a year now is because of the BTN money. Would be be able to outbid other, more attractive power conference basketball schools for a coach? Is this something we would not have been able to do when Pitino was hired?