I was a relapser myself and have also talked to many relapsers over the years. The story is always the same:
A complex constellation of circumstances, distraction by a thousand trivialities that, to the individual, seem to be of immense significance, numerous sensitivities, concerns, and objections that seem to stand in the way of promptly adopting this or that course of action, worries, resentments, alienations, doubts, factors that appear to license prevarication or delay, and endless other complexities.
But why did the relapse really take place? The answer is always the same: The individual did not take the actions set out in the book Alcoholics Anonymous, promptly, briskly, enthusiastically, and without hesitation, reservation, or deviation. And we're not talking minor dereliction: we're always talking eye-watering, systematic failure. The system withstands considerable alcoholic incompetence and is merciful to the surrendered but merciless in the face of wilful procrastination, dithering and dallying, outright rebellion, or self-indulgently nursed, concealed pockets of reservation.
How does one deal with this in another? Have a little chat. No more than 15 minutes. Post-mortem the relapse (always quick and easy: the reason is always lying in plain view); offer to show them the programme, starting now, then see what happens.
This is the crunch point: the individual must act, and act now, or retreat back into the subtle, highly tailored, and repeatedly failing smoke-and-mirrors system of meetings, telephone calls, talking, and tentative stabs at the programme that give the appearance of going to any lengths but are actually an elaborate deception to permit continued periodic drinking without the attendant guilt. Like the anorexic nibbling and moving food around the plate, where is the mere appearance of eating. The individual appears to be 'in the programme', 'on the road to recovery', but is gradually and inexorably deteriorating.
Faced with this choice, the person who, previously, was so talkative and concerned to communicate becomes evasive and elusive, almost invariably ghosts or beats a disarmingly charming retreat, with lavish thanks for the assistance and a promise to get in touch should the need arise.
What can be done? Nothing. Either alcohol will persuade or it will not.