你好.你的句子是定语从句.变成简单句就是：
Many people have married , and those poeple's chances to marry were much inferior to Miss Martha's.-------这样就容易理解了.
1 to do so == to marry .
2chances to do so were much + inferior 或者比较级 不是倒装.谢谢，我已理解，您可不可以再举个so这种用法的例子啊，好加深印象哦ok.
1Poor Mr. Smith who gets up so early every day has to do so to deliver milk to people's door before they go to work or to school.

2 She was absent from school and had to be so because her aunt was arriving from London.