Life, these guys are right. I asked 'Why' and I would still like to know the answer, but I am OK never knowing. The important thing is to get on with being the best person you can be, which includes continuing to be a great mother. You are all they have right now. It may not seem fair, but that is the reality, just as surely as if your h had been hit by a truck.
My h abandoned his children, and it really hurt them even though they were pretty much grown up.
If it helps, I believe that they are so focused on themselves [it is a CRISIS remember] that they cannot take the energy to consider the impact of their actions. Anyway, for whatever reason your h is ignoring his children, and they are hurt by it. You can't take the hurt away but you can help them deal with it in many ways. By dealing effectively with your own pain, by listening to them, and by occasionally telling them as much as is age appropriate if they are interested. By showing them that you are strong, and that it doesn't take another person to make you happy, you are teaching them a very powerful lesson. Children take in actions not words, just as the rest of us do. As adults we attach a lot of importance to words, and that isn't always wise!
Once you really shift the focus from your husband to yourself and your children the whole dynamic will change for the better, almost immediately. Trust us all on that. He is out to lunch and you are the ones that matter, also you can't do a thing about him.