I have a friend who all of a sudden was broken up with by their decade-long partner. Never saw it coming, never got full closure. Point is you can't look into someone's head and you might never get a definitive answer as to "why" and "how" and the sooner you accept that the sooner you can move on.
Sounds harsh now, but things end and this too shall pass eventually. Stay strong.
Yeah what's that about? Especially stuff like "TIL" has a lot of micro channels selfpromoting