Breaking-up is hard work. Though some might find it easy, the others will still come up with any reason reaching from significant to utterly ridiculous in trying to avoid that. “It would make him sad! She would cry a lot! We’ve got a flat together and a dog on top of that! What would his parents think?”
Even if we realise, down there, that it’s just bollocks, we will still be looking for some other way.
Now let me tell you a real story about a guy I once met, who wished to be deprived of his partner. Fortunately, the whole thing did not escalate as it does in the story, but still. He made the wish.
I should try to emphasise that what you’re about to read does not in any way comply with my perspective. It was merely a good plot; perhaps it just went too far. But that is the virtue of a story.