Because Swift 1.0 was far superior to Objective C in maintainability and code quality.
Now I do admit the build times were awful and I had a couple puzzling crashers that were only cleaned up by Swift 1.2 (thankfully didn't ship till after 1.2 was final), but the transition was worth it.
> Because Swift 1.0 was far superior to Objective C in maintainability and code quality.
You can take Objective-C code written three years ago, open it up in Xcode today, and compile it. The same cannot be said for Swift. So saying Swift 1.0 was "far superior" in terms of maintainability is a bit of a stretch, in my opinion.
Sure, in the edge case where you actually don't maintain code except for once every three years, it's closer. But even in that example, after a couple bad hours/days (given size of your project) updating your swift code, you then have many good days working in much more readable code.
Now I do admit the build times were awful and I had a couple puzzling crashers that were only cleaned up by Swift 1.2 (thankfully didn't ship till after 1.2 was final), but the transition was worth it.