In what way does Toohey's purpose in promoting mediocres like Peter Keating, Lois Cook etc integrate with his anti-Roark campaign?

The purpose of making mediocre work seem great, would mean that “great” would no longer carry any meaning. The destruction of greatness in the eyes of society, would mean that no individual achievers such as Roark would rise to prominence – this would make Toohey’s mission of combining the world much easier.