It is not uncommon that the relationship between a husband and wife will deteriorate while neither one of them are consciously aware of it and/or admit it to themselves or to the other party. Very often marriages will deteriorate for a long time before it is ever discussed between the parties. The fact is however that for a significant portion of this deteriorating timeframe the parties are aware that their marriage is deteriorating. Or one party believes the marriage is deteriorating and the other party “feels” something isn’t right. They are aware even before they admit it to themselves in any conscious way.
Sometimes during this period of deterioration, the parties will individually or jointly do things that don’t really make sense in light of this ongoing deterioration. This is when the last child can be born; this is when they go on a wonderful and expensive vacation; this is when they buy that cottage by the lake or this is when they put on addition onto the house.
All of these things would not have been done had they consciously thought that their marriage would be over in the near future.
It is also not uncommon that the party who did not file the formal divorce becomes angry or even bitter about the fact that the divorce is happening so shortly after one or more of these things was done. Sometimes this party will believe things were done intentionally to take advantage before filing for divorce. Sometimes that does happen. Often the case is otherwise.