Nobody was listening

I watched the guy with amusement. He carried a loudspeaker and was shouting at the top of his voice. It was annoying. Everyone at the bus stop was irritated.

But this guy kept preaching and preaching only to have everyone ignore him.

No, they didn't ignore him. they were irritated by his noise. Not his message. Just the noise that the rambling megaphone was making.
 
When you try to pass your message across, try to avoid getting your message lost in the medium conveying your message.