The answer to this question can be found in chapter 11. This chapter begins with Stanley doing a little bit of pouting. Mr. Pendanski did not find Stanley's fossil worthy of giving Stanley the rest of the day off, so Stanley is pouting over his bad luck. As he gets back in his hole to start digging again, X-Ray comes over and wants to talk. X-Ray wants Stanley to give him anything that is found in a hole that Stanley is digging. Readers will see at this point that Stanley internally wonders why X-Ray is the leader of the group, but Stanley doesn't explore that thought until digging again.

Stanley is happy to give X-Ray anything he finds. Stanley reasons that it is better to stay on X-Ray's good side than bad side. That's a good rule for how Stanley interacts with all of the boys, but it is even more important with X-Ray, since X-Ray is the leader. Stanley once again wonders why X-Ray is the leader since X-Ray is practically blind, isn't the biggest kid, and isn't the toughest kid, either.

It was a little surprising, he thought, that X-Ray was the leader of the group, since he obviously wasn't the biggest or the toughest.

Stanley and readers will eventually learn that one of the reasons why the other boys look to X-Ray for leadership is because X-Ray is willing to put himself at risk in order to protect the other boys. X-Ray has a natural ability to defuse potentially difficult and contentious situations. X-Ray also maintains a leadership position through a rewards system of sorts. X-Ray will be nice to you if you are nice to X-Ray, so it benefits everybody to be nice to X-Ray to earn his protection.