Look at your vector diagrams - angle of attack is between the Pitch angle and the relative air flow. RAF is a combination of rotational airflow and induced airflow. Change the induced AF, you change the AoA (for a constant pitch angle)
If the RAF comes in from a different position, but the AoA is the same, then the pitch angle has changed, because of a different induced airflow.
Pitch is connected to Power via the governors, and it changes because the power required to overcome induced drag has changed.