As we discussed already, Objective-C was previously the primary language for developing on Apple's platforms. This means that Objective-C had a lot of influence on Swift; the largest of which is that Swift was designed to interoperate with Objective-C. Swift code can call Objective-C code and, likewise, Objective-C code can call Swift code.
Ultimately, Swift was designed, and is still is being designed, to be the next step in programming languages, without having to throw away all of our Objective-C code. Apple's stated goals for the language are for Swift to be more modern, interactive, safe, fast, and powerful. These words would be pretty much meaningless if we didn't already have a baseline to compare Swift against. Since Swift was designed primarily for Apple's platforms, that baseline is largely Objective-C.