In the late 1960s, an MIT student went to a meditation class by Philip Kapleau, author of the classic, The Three Pillars of Zen. The student only went because his Ph.D. advisor had invited the speaker to campus.
No word on whether Roshi Kapleau was discouraged to see only four listeners in the large lecture hall, the organizer, his student, and two others. We do know that he effectively delivered his message because that student became Jon Kabat-Zinn, the most influential promoter, teacher, and scientific researcher of meditation in the history of the West.
It is not a speaker’s job to judge the audience. We save the world one speech, sometimes one listener, at a time.