Dad Died With 2.5 Million, Mom Who Divorced Him Years Ago Claims She Is The Sole Beneficiary

Location: Arizona

My dad unexpectedly passed away last week and our family wrecked. He worked hard for his family and saved for a retirement he never reached. Around 2016 my mom divorced him and while I don’t remember all the details, she got about 600k of his retirement along with 3k is spousal maintenance. She raided her retirement and in about 5 years it was all gone. She is horrible with money, there are no assets. Rents, has a car payment. All of it gone.

My dad was crushed by the divorced, but his age and not really having any friends besides his family he never updated the beneficiary on anything and we all continued being a family weirdly enough. His house which he owned is confirmed in my mom’s name but the life insurance and bank account is unclear. My mom claims she is the sole beneficiary and almost seems giddy, already talking about upgrading the house, paying off all our debt and stuff, it’s horrible. My dad is gone and all that’s left is his life’s work and I refuse to believe my mom who divorced him gets everything??? I looked up a bit and saw one Arizona law that automatically revokes beneficiaries on divorce but it seemingly doesn’t always apply.

Is there anything I can do to challenge this? My mom will spend all of it in 10 years and we will have nothing except our family home. I love my mom and she is well meaning but she’s seeing dollar signs and it’s painful to even listen to this right after my dad’s passing. I have 2 siblings. We are all adults.

Any information would be helpful, most importantly is it really possible for an ex spouse to get 100% just because someone didn’t update all their stuff?

Also I’ll add that when we went to the funeral home to confirm information on the death certificate it was already marked that he was married. I corrected it and my mom got awkward saying they planned on re-marrying (kinda true but still irrelevant). The guy quickly shut that down and changed it. No idea if my mom was trying to commit fraud.