If they rarely lived at the house, and he kept them in one room, she may not have ever known they were there. If he had a good sized gun safe, or even just stored them under the bed or in the closet. (It happens more than you'd think, that s/os have no clue what's in the house). It's said he had tannerite, too. Tannerite is usually in a container that reads Rifle Targets or Exploding Targets. If you aren't familiar with Tannerite, and what it can do, look in YouTube for "1/2 pound of tannerite vs fridge". That's just a half pound. When I saw he had Tannerite, I wondered what he decided not to do, or didn't have time to do. But it wouldn't be something that she would necessarily know what it was.
Maybe his wealth was through ill-gotten gains, and the gambling was his way of laundering money, and he got wind something might be coming down on him soon, so he decided to go out big?