Why are you required to stop now?

You are required to stop because of the electric scooter. In German traffic rules, electric scooters are treated similarly to pedestrians in many situations, especially when they are crossing or about to cross a road. You must yield to them to prevent accidents and ensure safety. Even if pedestrians or trams are present, stopping is specifically mandatory here due to the scooter's presence and right-of-way rules. This means you must wait until the electric scooter has safely crossed before proceeding.