I'm an American who loves Jane Austen, the Brontë sisters, Charles Dickens, Daphne du Maurier...the kind of books (and movies) that helped create the tropes this show mocks relentlessly and hilariously.
You get such tropes as: the perfect and incomparable dead wife, conniving housekeeper, huge terrible secret, clueless vicar, physically wretched but eternally optimistic and naive character, deformed villain, straight man with curiously close male servant - the list goes on and on. The show isn't "cruel," it's making fun of the stereotypical characterizations gothic novels loved to use to create tension. And some of those characterizations were based in really messed up ideas from the 1800-1900s, like that ugliness was an external reflection of evilness or bad character, or that virginity was the most important attribute in a wife (who cares who she is as a person?). It's making fun of the ideas in those stories that are abhorrent or cliche to us now.
In the first episode, Helene is set to marry a much older pastor, and he tells her that if she wasn't entering the marriage as a virgin, he would of course have to stone her to death by his own hand 😔. I laughed out loud and was hooked from that moment.
But it's probably not funny if you don't know the stories it's mocking, because satire relies on familiarity with the subject matter. It's "dumb" humor in the vein of Scary Movie, Walk Hard, Hot Shots, Robin Hood Men in Tights, Blazing Saddles, etc. The jokes are rooted in all the OTHER media you've watched and the stereotypes they're built on.
If you've ever wished Young Frankenstein could have a baby with Wuthering Heights, this one's for you.
