The book Beowulf is about a viking village that gets attack by two ugly monsters, Grendal and his mother. The first attack happened when everyone was asleep. Grendal snatched two people and brought them back to his den. Before the next attack happened, Beowulf and everyone else pretended to sleep so when Grendal attacked they would be ready. Soon enough Grendal came and Beowulf jumped on his back. About five minutes of trying not to fall off, Beowulf got a hold of Grendal's left arm. He started pulling. Tearing skin, tissue, and, muscle, Grendal's arm snapped off! Grendal left to his den. When he got there, he died from loss of blood, his mother wanted revenge. The next night the vikings went to the lake and Grendals mother pulled Beowulf down into a cave. Beowulf sliced her head off. as soon as the rest of the vikings were getting worried, Beowulf bobbed out of the water holding the head of the monster. Beowulf killed a dragon, but his arm got stuck in his mouth, so he had to cut it off. Beowulf died from the loss of blood, but thanks to him, the vikings got all the dragon's gold.
I had two questions and a reaction.

My two questions were one, why didn't they just lift the dragon's mouth open instead of cutting his arm, and two, why did Grendal attack in the first place?

My reaction was surprised because he could've opened the dragon's mouth.