It’s more insidious than that:

https://piped.wireway.ch/watch?v=5RpPTRcz1no%3Fsi%3Dfev-OzgZmzcUfsPW&t=1

I read in another article that the dog that died had recently come back from a medical procedure at the vet, and was being kept in a crate. The two that survived had access to a dog door so presumably were able to get food/water outside.