Acceptance of new ideas is usually contingent on three preconditions: (1) the world must be ready for them; (2) they must be convincingly advocated by a persuasive person or group; and (3) they must be perceived as clearly superior to (or, at least, not in serious conflict with) other widely held beliefs.
Oasis in Space: Earth History from the Beginning, Chapter Three (p. 49), W.W. Norton & Company, Inc. 1988