What is your theory on why Grendel let hrothgar live? He needs to fight with all the other people Beowulf ​

As a preface to telling the story of his war with the Danes, Grendel recalls the growth and social development of men. In the beginning, nomadic tribes of men roam the forest. Occasionally, two bands of men meet in the woods and battle each other, and when they are finished they crawl back to their separate huts and caves and tell wild stories about what happened. When the bands grow larger, they settle in particular areas and set up large communal halls. The insides of these buildings are beautifully painted and decorated with tapestries and woodcarvings. The humans plant crops and domesticate animals; women stay at the camp to tend to home and field while the men go out each day to hunt. At night, the humans drink and tell stories about what they plan to do to neighboring halls. Each band follows a similar pattern of development, and Grendel watches them all. He is amused by their drunken boasts about conquest, and believes that they are only partially serious.

Explanation:

he has become more humble and patient in battle.

the answer that is correct is the last option.