They agree with each other, defend each other, and somehow always seem to land on the same side of every decision. If you're outside that group, getting anyone to seriously consider your idea is a different story. I've seen genuinely useful suggestions get dismissed without much discussion. Then someone from the inner circle says something similar later and suddenly everyone thinks it's a great idea.
After seeing that happen enough times, you start wondering why you bother speaking up. It's not that there aren't smart people here with good ideas. It's that the right people aren't always the ones being listened to. Eventually people get tired of fighting that battle and just keep their thoughts to themselves. And that's how things continue going in the wrong direction.