When it comes to escape velocity, mass isn't the only factor. 11.2 Km/s is Earth's escape velocity at the surface. Its lower the higher you go. This also applies to any object wanting to become a black hole, because if you have something that's a hair away from having the right density to become a black hole (the volume in this case being of the space within the event horizon), its just gonna ever so slightly collapse on itself under its own gravity and become a true black hole.