Why is Ralph voted chief?

There are a larger group of boys around Ralph than Jack’s choir. Ralph is also holding the conch. Having blown the conch, Ralph is automatically linked as an authority figure by most of the boys. There were also other traits that set Ralph apart,

  ..there was a stillness about Ralph as he sat that marked him out: there was his size and attractive appearance; and yet most obscurely, yet more powerfully, there was the conch. The being that had blown that, had sat waiting for them on the platform with the delicate thing balanced on his knees, was set apart.

Ralph was close enough to the boys’ recollection of adult authority to give him the role of chief.