Turkey had an election a few month ago, and Erdogan is in the "Turkey Stronk" party. So they have to look like they're "coming down" on Sweden for bonus points. Now that he's been re-elected, he can stop burning what little international goodwill Turkey has left.
Also stupid, he was never going to get f35s and everyone around him has them.
Should have played it cooler, taken the f35s, s400s do him no good against anyone he's pissed at, he should have known it then, it's proven beyond a shadow of a doubt now.
At this point I don't understand why he doesn't just offer to ship his s400 to Nevada in exchange for F35s, since the platform is very clearly little more than strongman bait. I guess that would require him to admit he got duped.