What happens when renters get a divorce?

If they do get a divorce and neither of them decides to stay, they will probably choose to sublet the apartment rather than break their lease. If one of them seems like less of a violent alcoholic you might try just casually asking what they plan to do with the apartment. If they say sublet it, you could then mention your interest. However, subletting from them would mean dealing with them, which might turn out to really suck. If one of them was already renting before the divorce he/she might choose to stay; usually when people move out after a split it's because they can't afford the rent on their own. Doesn't sound like that's the case here.