Why are you required to stop now?

You answered correctly. You are required to stop because both the cyclist and the confusing traffic situation demand extra caution. In German traffic law, whenever your view is obstructed—such as by a parked vehicle blocking your sight into the intersection—or when cyclists may cross your path, you must stop or slow down significantly to ensure it is safe to proceed. Even if you see a truck approaching (which is also important), the main reasons to stop are the cyclist and the unclear situation, as you cannot fully overlook potential hazards. This principle helps prevent accidents when your visibility is limited or vulnerable road users like cyclists are nearby. When you encounter unclear or complicated situations at intersections, especially when you have restricted view, always be prepared to stop.