I agree, this is a bigger and really dense cluster, but remember that e is just the average (mean) cluster size. There will be clusters bigger than it.

My point is simply that our intuition of randomness biases us to see meaning in clusters when there is none in the first place. In other words, we need to intentionally shift our prior on how unlikely this event is. Yes, it's still unlikely, but it's not as unlikely as you would think.