Answer:
Because Grendel's mother was not human, she was greatly feared by the Geats. When she was eventually killed by Beowulf, an Anglo-Saxon, the Danes' (Götaland's) fear of Grendel's mother became less as it was exposed that she too could succumb to the cold hands of death. She was not immortal, afterall, as they had previously feared.
Step-by-step explanation:
Beowulf was an English epic poem which chronicled the military exploits of an Anglo-Saxon named Beowulf. Through sheer doggedness, Beowulf mustered the unflinching courage to kill some monsters: Grendel, Grendel's mother, and the dragon named Wiglaf, who were making life unbearable for the Geats. Following his invitation to fight Grendel by the king of Götaland, Hrothgar, Beowulf showed the stuff that the Anglo-Saxon was made of. As it was known, the Anglo-Saxons preferred to die rather than live in subjugation. They fight for renown and to win laurels, instead of living in cowardice.