The larger the aircraft, the less likely it is to require any kind of key to start. The engine start sequence is not that complicated and the checklists are not hard to obtain. I don't know about that specific model but I've seen add-on models for Microsoft Flight Simulator (2000) that were detailed enough to require the actual start-up procedure to fire the engine. I'm not all that surprised that he could get the props turning.
Once the plane is pointed down the runway, getting it airborne is a simple matter of shoving the throttles forward and waiting for enough airspeed to rotate off the runway. Getting an airplane off the ground isn't the challenge. Putting it back on the ground in a condition that it can be flown again is the trick.