Just to add to the chorus, I know it sounds unfair and it feels that way in the short term, but in the long term all will be revealed.
As others have mentioned, it's a remarkable trait that active As hate to be alone and need a SO in their lives at all times (something I didn't expect but found as a common thread around here). Since they don't divert much energy into anything but drinking when they were in a relationship with you, because they didn't have to, they quickly find a way to put time into quickly filling the void of another person in their lives once you are gone. Amazing actually sometimes the level of effort and speed that goes into quickly being paired off to avoid having to face the damage that was done to break the relationship with you.
I don't wish ill upon my ex but I also wished she would channel her energy into a recovery program instead of just starting the cycle over with a new person. But finding a new partner (to try and forget/avoid their past mistakes and the depression of losing us) and continuing to drink (because it's what they do) is the easy way out and typically the path that is chosen.
In the end, when the dust settles, we always prevail.