Why does Eurymachus get so angry when he cannot string the bow?
The answer to this can be found in Book 21. I would not really say that he gets angry. I would say that he becomes sad. He sighs and he says that he is "grieved." Here is the quote:
He heaved a deep sigh and said, “I grieve for myself and for us all
The reason he feels like this is because he feels that his failure has taken away his honor and his pride. He is supposed to be a great warrior and strong man, but he cannot do this thing that Odysseus is able to do. He feels that it will make him seem like less of a man.
what I feel most is the fact of our being so inferior to Odysseus in strength that we cannot string his bow. This will disgrace us in the eyes of those who are yet unborn.”