请帮忙讲解一下这个英语句子的结构,以及前半部分的两个by的作用~Frustrated by the old-boy network by which Minnesota judges were always appointed ,Page challenged the system in court and was eventually elected judge in the Supreme Court

Minnesota judges were always appointed by the old-boy network,
Page was frustrated by the old-boy network so that he challenged the system in court and was eventually elected judge in the Supreme Court
不知道这样写你能理解吗，

by the old-boy network是介词短语做状语修辞frustrated，by which...是定语从句修辞the old-boy network的，主句是Page challenged the system and was elected judge...

　　An old boy network,or society (also old boys' club),can refer to social and business connections among former pupils of male-only private schools.校友关系网　　明尼苏达州的法官本来总是由联谊会任命...