It's probably somewhat of a "honeymoon period"--some people call it the "pink cloud". Everything just feels so TERRIFIC, it seems like everything is gonna be great from here on. What happens then is just... life. Life on life's terms, which can sometimes suck. And alcoholics are used to coping with sucky things by... drinking.
Now, people who are really committed to recovery learn to deal with the sucky aspects of life. But they don't always do it gracefully or happily--especially at first, when they are still getting used to it.
My first husband has now been sober 31 years--he went through his sometimes rocky moments in early sobriety and has wound up being one of the kindest, best people I will ever have the privilege to know. So it CAN happen.
Just be ready for moments that can be difficult. Sometimes there are slips, but sometimes not. Wait and see. More will be revealed.
Are you going to Al-Anon? It can help a lot if you're working a program, yourself. It will help you avoid the temptation to be too "helpful" with stuff he needs to be learning for himself, with the help of other recovered alcoholics.