这里he 是正确的,而不是省略了by. 如果是by he,那么比较的是两个世界 a world dominated by wealthier, better-educated, and more polished people a world dominated by he 世界只有一个,并不具可比性。所以这里 dominated by wealthier, better-educated, and more polished people than he.都是修饰成分,其实比较的是 people 和 he
a world dominated by people (who are wealthier, better-educated, and more polished than he is)
比较对象的判断:如果是by people和by him比较的话,其比较的结果应该是修饰dominate的,比如world more difficult dominated by people than by him,但是此题比较的结果是wealthier, better-educated, and more polished,说明是people和he在比较,原句为:People who were wealthier, better-educated, more polished than he was(因为这里的he不会被误认为是宾语之间在比较,所以助动词可以省略);