It's impossible to say "why" anyone would take their life Chickippo...sorry for your terrible loss.
Don't try to "blame" anyone or any group for the tragedy. It's easy to second guess in these types of situations. Could his mental health team have done more? Certainly - but it could have made things worse too. Could he have done more in AA? Sure..but that is no guarantee that the outcome would have been any different.
If AA works for you continue to use it help you heal. I'm sure there are many others with the same feelings you have, grieving is part of the process that hurts..but it's necessary.