I disagree. Purdue is one of the 20 or so athletic departments that do not take subsidies from the university. In the past 35 years, they've had some uncompetitive eras (Akers, Colletto, Hazell, Walters) and some competitive eras (Tiller, Hope, Brohm). Purdue was 8-6 in 2022 and 9-4 in 2021. That includes wins over #2 Iowa, #3 Michigan State, and two more top-25 upsets - and that was not very long ago.
I attended both the UND and Nebraska games this year. Both were sold out. Northwestern also sold out. The other home games were within 4k of capacity. The support is there. The product this year was bad - and they took a step toward fixing it today.
The right coaching staff (see Indiana) can turn around a perennial doormat rather quickly these days. They lost Scourton (10 sacks in 2023) to aTm (6 tackles last night) and several other players to the likes of Aggy, Vandy, and MSU. Deion Burks (top WR) left for OU. To me that was a sign that Walters was in trouble: top players leaving. It may be supporting your point of NIL, though, but we shall see. A competent coaching staff gets at least 5 wins out of the roster there. And a competent coaching staff also recruits better and builds a program.