man-eating may have started because people were eager o become as strong and brave as their anemies

Question

1.may have started是情态动词跟现在完成时，表委婉？
2.to become as strong and brave as their enemies是不定式短语当系动词were的状语？

Answer 1

这里的may应该是用来表示猜测的意思，就是可能、也许这样的，或者用大概来翻译，这样感觉好些。
be eager to 是一个词组的，就是热切想做,渴望要做
because引导的原因状语从句中，become as strong and brave as their enemies算是主语people的补足语吧，这里相当于I want to do sth的结构