Why did Thomas think Chuck may be his only friend there?

Chuck was the only one who accepted Thomas, although Chuck ribbed him just a bit, as the others did. None-the-less, Chuck was the only one who had patience with him, which isn't surprising as Alby had put him in charge. In the midst of chaos and in view of "the changing", Thomas is very frightened (and sick to his stomach), Alby becomes very angry, and Chuck is there to depend on.

What did Thomas observe about the Maze and the Runners in Ch. 4?