Tartan was sold in a panic mode. An activist investor (Nelson Peltz) went after Dupont for allegedly losing money on its golf course, hotel, etc. Under pressure from people like him, Dupont dumped these at well below market value because they were trying to appease the activist (it didn't work as he appointed his hatchet man the next year).
Inge tried to avoid the same fate and made the decision to dump these properties. Problem is the buyers lowballed because they knew he would sell it to avoid someone like Peltz making a run at breaking up 3M like Peltz and his henchman Ed Breen is doing to Dupont.
Five years later, Mikey is breaking up 3M not because it couldn't exist as a conglomerate but because he needs the cash to pay for earplugs and PFAS and maybe Bair hugger too.
Inge should have told activists to pound sand. He got the stock up to 259. There was no pressure like there was on floundering Dupont.