Objective-C has been open source for even longer, and Cocoa and the associated mobile toolkits eminently clonable. I'm rather more surprised that Google didn't

Objective-C has been open source for even longer, and Cocoa and the associated mobile toolkits eminently clonable. I'm rather more surprised that Google didn't make an 80/20 iOS compatibility toolkit 15 years ago. If they didn't do that then when iOS was dominating the hearts and minds of pretty much every developer behind any noteworthy mobile app, then I wouldn't expect them to make Swift a first-class priority today, when Android has basically "won" on the global scale.