The guilt is validated by the negative things they perceive from having been in the marriage. Some is real and some is exaggerated. Our reactions, if they are extreme, bitter, angry, vindictive, blaming, etc... are used to fuel what they thought was negative in the marriage. If this is our reaction, it makes it much easier for them to live with the guilt (because, as they would reason, we were such "A-holes" to begin with... In other words, it's much easier for them to excuse themselves when our behavior can be shown as worse. OP "saves" them from an intolerable situation, and a spouse who appears to be a raving lunatic).
There is no arriving, ever. It is all a continual becoming.