I think Campbell is using this as a PR play to further bolster his interest after next season to drive up the price based on having multiple suitors at the auction. He's coming back for another year at Iowa State, and based on how things shake out this coming year with firings or coaches leaving for NFL/other college positions, I think he's going to be at one of these schools for the 2022 campaign: Michigan, Penn State, Tennessee, USC, Notre Dame, or Nebraska for the 2022 campaign. He'll use NFL interest as a smoke screen.
He's a college coach. He's about details and discipline, and I don't think NFL egos will subscribe to his discipline/culture nearly as well as college athletes do.