The real reason was the pressure to be a national championship contender which caused them to fire coaches who were loyal to Wisconsin and doing a pretty good job in pursuit of a radical program change that would supposedly vault them to the next level. This just happened to occur at the same time as NIL, which gave the programs with the biggest donor/sponsorship bases a huge advantage that they didn't previously have.
It's ironic that we pointed and laughed at Nebraska for making a similar foolhardy pursuit, and now the same thing happened to us. Except Nebraska now has a better chance to actually improve because of their ability to finance NIL deals.
And meanwhile, the playoff expanded, so if Wisconsin would have just continued to win at the level that they previously did, they would have no problem making playoff appearances. But those days are long gone now.