The primary feature of Swift is that it a more safe language (via many of the same mechanisms in languages you referred to above), while being extremely compati

The primary feature of Swift is that it a more safe language (via many of the same mechanisms in languages you referred to above), while being extremely compatible with the extremely large API surface area of iOS/macOS (which is both in C and Objective-C), and allowing incremental adoption without having to rewrite existing application/library code. To have adopted any of those other languages requires dramatic changes to a huge amount of platform APIs, along with on-going challenges of divergence. Put another way, any other language would have basically forked the entire platform. The Swift developers definitely have ambitions beyond being a compatible with Apple's existing SDKs, but that's the fundamental thing Swift does that no other language can do.