Why Google and Apple made their own programming languages

Apple: was afraid to loose developers to Xamarin (once it becomes more stable). Failed to deliver a fast language, failed to deliver an open-source language in 2014 (!).

Google: starts using / creates a new language every few years - C++, Python, Java, Dart, Go. Failed to stick to the vision of native Dart support inside of Chrome, Angular team deflected to TypeScript as a better alternative, Go - quite limited, e.g. no generics - nowadays(!), useful if you cannot use other options due to "religious" views or the situation.