Excessively cruel or sadistic author?

Okay. Is it just me, or is this needlessly cruel on the part of an author to their characters?

I will keep the names of the book, author and characters anonymous because I am still reading the book.
I’ve had problems with the novel thus far and what the author has done (despite some of the novel’s strengths) but this made me wonder if I really like the novel or not.
What do you think:
King of a Kingdom, long a widower, sends for a bride from an outland province of his kingdom. She doesn’t speak his dialect and is clearly going to be homesick. So, he decides to build a church in the style of this outland province to make her feel at home. As a sign of permanance, he decides to use iron nails rather than wooden dowels in the construction of the church and its furnishings.
The new wife is delighted, loves the place.
Five years later, while in the church, the wife is startled by her young son.She scratches her hand on one of those nails that hold the church together. She gets tetanus, sickens and dies.
You tell me: Excessively cruel, or just tragic?