Beowulf, the Swede

Since my little daughter is studying to become an English teacher, I am learning in parallel to help her write papers. We are by far the best students of her class. To succeed, I am faking an extreme leftist, feminist, diversity loving PC worldview, but I am truly interested in English literature. 

I never realized that the first English language literary work - Beowulf - was about a Scandinavian hero, a Swede, in fact. The language is considered English, although I did not understand a word and the English - except Offa - are absent in it. From the technical point of view, the poem is written in alliterative verse, that is, the repetition of initial sounds of words.  Like Spiro Agnew's  "nattering nabobs of negativism." 

Beowulf sails from his home in Geatland (South Sweden) to aid the Danes in their conflict with a monster, that has burned down their  communal beer hall. In short, the Swede kills the monster and his mother too with his sword Hrunting so the Danes may continue getting drunk safely. 

How is that this small primitive clans developed into the great English nation, that brought us the Industrial Revolution and civilized the planet? I have to learn more to discover the connection.