Hrothgar's men would dearly love to take on Grendel. After all, the big slavering monster has wrought merry havoc on the Danes, wiping out so many of Hrothgar's best warriors in his regular raids upon Heorot.
But the sad truth is that none of them are strong enough or brave enough to take on such a mighty task. Hrothgar's men may be perfectly good for fighting in battles against rival tribes. But those tribes consist of men like themselves, whereas Grendel is not a man at all, but a monster—and a very powerful one at that.
It soon becomes apparent that only an outsider will be able to take on and defeat Grendel. Such a man will need to be possessed of not just limitless reserves of strength and courage, but almost superhuman powers.
For the job at hand, no ordinary warrior will do. This means that no Dane is up to the task at hand, for there are no such warriors under Hrothgar's command. Only a foreigner can possibly step into the breach and challenge this bloodthirsty monster.
(The entire section contains 4 answers and 673 words.)