Hurin's land has been overrun by Easterlings; everyone's enslaved and oppressed. It's an occupation. One wonders how much Tolkien's experience of the Great War informed this section.
The 'first strand of the fate of Turin' is woven when Morwen, his mother, chooses not to go with him to the Elven refuge of Doriath. She's willing to send Turin there to be fostered, but not to take refuge herself 'as a beggar'. Morgoth's curse works by taking virtues and twisting them, making evil out of good.
Evil being a mockery of good keeps cropping up. The Easterlings, Sador says 'have learned quicker from the Orcs than we learnt from the Fair Folk', mirroring the relationship of Hurin's people to the Elves with the Easterlings and the orcs. Earlier, Sador was carving a chair for Hurin; now, Hurin's got a new chair, but it's a chair of stone above Thangorodrim.
Everything in the story turns to darkness and tragedy.