I don't buy the argument that 'we could have had him for free' this summer.
There's every reason to believe Chelsea would have done what was necessary to avoid a free exit. He's young, English, international, POTY x2 - that is a 50-80+ million pound asset every day of the week. The increased contract spend (they offered him 200k, so just 50k more) would've cost them roughly 5-10% of the transfer fee they'd make, potentially even a bit less.
If we had not purchased him, I fully expect they'd have secured him on a new contract and sold him for as much or more in 1 or 2 seasons. But they didn't have to, because we were there with an offer. I suspect he and his agents knew that too, but that he felt insecure about his playing future at Chelsea when they offered only a 1-year extension. So he decided to pursue a longer-term project and contract.
As for us, I'm looking forward to seeing more of him.
He's been recruited to do a role he's never really done before (#8). His defensive stats from last season suggest he has the attributes to do it, particularly in a high-pressing team. So he may need a full, fit season to gel with the team and understand his new role. I think we'll have a clearer picture of whether his evolution is effective around the second half of next season.
And even if it's not, he's got the tools to be successful elsewhere on the pitch - potentially as an option in any of the three slots behind Hojlund.
Bottom line, it's early days and I think there are several paths for him to become a success for us.