Sure, talent wins games, but we're talking about a forward with 10 points vs a defenseman with 6. Dach is 18 while Cholowski is 21, so Dach has a higher ceiling, absolutely, but over the next three years would you rather have Dach and Seabrook, or Cholowski and a 6Mx3year UFA? No idea who that would be, but lets hypothetically call him, "Gustafsson."
Because Seabrook's remaining compensation is mostly signing bonus and not salary, it looks like buying him out means he earns 17.7M to not play hockey the next four years, instead of 20.5M to play them. The team buying him out only saves 300k in cap hit next year, and in 22-23: https://www.capfriendly.com/buyout-calculator/brent-seabrook/2020-06-15
So Seabrook isn't being bought out any time soon. Can Detroit offer him a more exciting role on a more exciting team than he's got in Chicago, where he's won a Cup and the team is just ahead of the Maple Leafs in the standings, today?
I would take Dach and Seabrook any day of the week over Cholowski and a UFA at 6M. Go look at what 6M gets you in free agency, like straight up real free agency. Zuccarello, Myers, Stastny, Turris, Radulov, Shattenkirk, Lucic, Ericksson, etc etc etc All players who by the end of their contracts are overpaid themselves.... sure they're probably not so bad for the first couple years but Chicago isn't looking at the cup run the next couple years anyway so whats the rush?
Dach has the potential to be a top flight elite player. Cholowski not so much, good but not elite. Frankly many Wings fans are getting a bit over him to boot so its not like they are offering up their prized possession or anything.
The buyout of Seabrook would not be for cap saving, it would be for getting rid of his roster spot and letting him go on to other pastures without holding him down as a 7th dman for the rest of his contract. A mercy for a former stud of the team. That's if they felt like they needed to get him off the team. They could simply just keep him for a couple more years as a veteran leader on the team. Hope for a compliance buyout or maybe a change in the buyout terms or simply buyout him out at a later time normally. They actually get some decent savings in 21-22 and 23-24. Not perfect but not buyout proof either.
Cap space can be maneuvered, manipulated, moved around to make the salary cap work. Adding a potential top line center? How often does one of them come along, what impact to they give their teams and what are their price tags to acquire? There are so many ways to make your salary cap work in today's NHL that simply keeping the player and not losing the talent is way more advantageous.
Also keeping Seabrook leaves open the option that a miracle happens. Maybe he starts playing better, maybe he decides to retire, maybe he gets LTIR'd, maybe someone is stupid enough to trade a less headache player to them in exchange for him. All potential outcomes that help the Hawks and let them keep their potential stud player in Dach. I joke but technically all those options have happened before so its not that far-fetched.