Jobs licensed Objective-C for his Next Computer project, and kept with it even after the hardware was abandoned. When Apple purchased Next, Objective-C became the de facto development language. Objective-C, though, is an old language with a history dating back to Smalltalk. It was created before C++ really took off, and it's a tough language to master.
Swift, a replacement for Objective-C, was introduced at WWDC and is already gaining traction with developers for being lighter, faster, and having a lot more built-in security. Many classes of errors will be impossible, reducing the number of crashes. This language was needed and it's doubtful Jobs would have given it the green light.