Which excerpt are we referring to with this?
the boys use the sticks and rocks to start the fire
The connotation is that the pants did nothing to meet his expectation of what pants should do.
A typical epic hero must perform heroic deeds. Beowulf kills Grendel, Grendel's mother, and the dragon, all of which are heroic deeds that no one else was willing to take on. The foes that Beowulf fought were all beyond human strength and capabilities and required superhuman abilities to bring down. Beowulf embodies several traits that make him a textbook epic hero. These include superhuman strength, his courage in the face of extreme danger, and his loyalty to both his superiors and to the men who serve him. An epic hero is not perfect or immortal but he is sort of super human. He is larger than life in the sense that his qualities exceed those of regular humans. For example an epic hero will have extraordinary strength. Beowulf displays this best when he fight Grendel and rips his arm from his body. Grendel is an imposing beast who has already easily destroyed a number of men, including warriors who are strong and experienced fighters. Beowulf's feat in killing Grendel perfectly displays how his physical strength sets him apart from others. He is also incredibly brave and willing to place himself in danger to save the lives of others. Initially he nominates to go to Hrothgar's kingdom of his own volition, despite knowing the horrific reports about the damages that Grendel has caused. He seeks out Grendel mother in her cave so he is placing himself into a foreign environment to face off with an angry, volatile monster. Later in his life, when he is much older, Beowulf sacrifices himself fighting a dragon to protect his kingdom. Lastly Beowulf is loyal to his superiors and to the men who serve him. Before he enters into any battle or fights any monsters he makes certain that his men will be taken care of. He is their lord and they have sworn their fealty to him. Beowulf is repaid by one of his men, who finishes off the dragon after it has mortally wounded Beowulf himself. His men also honor him posthumously by memorializing him as the epic hero he has proven himself to be. This is the truncated answer to your question.