Her baby father (Zeus), aka the big douchebag, married away her daughter Persephone to his brother Hades. Patriarchy does what patriarchy does. The brothers were aware neither Persephone nor Demeter would approve of the deal so Hades had to kidnap Persephone and force the deal upon her.
So Persephone were abducted and her mother were beyond herself with worry about her absence. Once Demeter learnt about the deal she threw the hissy fit that all hissy fits are measured against. Plants stopped growing, livestock stopped giving birth and the world soon was in a cataclysmic state. Behold a mother's justified wrath and tremble.
Douchebag-in-chief was forced to negotiate but wouldn't anull the whole deal. Only that Persephone would spend half her time with her mother (spring, summer) and the other half with the husband forced upon her (autumn, winter).
What I especially like about their content is that there is plenty of source critique. Things are seldom presented as "this is the exact truth". Mentioned in the video about Hades and Persephone is "we don't know the original myth" which I find telling of much of their mythology work.