Positive expectations shape both people's performance and how the leader treats them (the Pygmalion effect). The leader shows people they believe in them, makes goals and ground rules explicit so effort is focused and feedback is possible, and provides and seeks feedback, since motivation rises only when a challenging goal is paired with feedback on progress (either one alone achieves little).
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.