Swift uses the Objective-C runtime.
Swift can uses the Objective-C runtime for interoperability with Objective-C code, just like .NET uses COM on Windows.
They need to interoperate with the rest of the platform.
Re:Brad Cox has died
by microtherion on Saturday January 23, 2021 @10:42AM
(#25882994)
Swift is tiptoeing between static and dynamic typing, preferring the former when feasible, but often needing some of the latter when dealing with the UI.
"Advancements in the Objective-C runtime"
https://developer.apple.com/videos/play/wwdc2020/10163/