Speech and Silence
Answer: The Chafetz Chaim was once approached with a similar question by a Jew who spoke for a long time to a packed synagogue but failed to see how even one Jew had improved as a result. This is what the sage answered:
"One never knows when his words will have an impact. The Torah commands us to 'place these things on your heart' in the hope that in time they will eventually be absorbed into your heart."
He then added another benefit of speaking to an unresponsive audience for a very long time:
"I'm surprised at you," replied the Chafetz Chaim. "Don't you know what the Vilna Gaon writes from a Midrashic source about silence? He says that for every second which a person holds his silence he merits the Hidden Light which is beyond the comprehension of even the angels. All this for just one second of silence! Now imagine how great is the reward for an entire audience being silent for two whole hours! What more do you want?"