That's one reason criminals are criminals in the first place - they think they can get away with it, that they're somehow better than others, too smart, too whatever to get caught or face the same consequences as all the other criminals.
After more thought, can you really believe that they didn't know the dangers of the drug business? Even we know the dangers and I assume that we don't live that lifestyle? Do you think they didn't know or hear of any other dealers getting "jacked"? They never heard of innocent children being killed in drug related crimes? -- think drive-by's, accidental overdoses, losing custody of kids because of criminal and/or drug activities. WE have certainly heard of all of those, as well as of entire families being killed over drugs.
No, I'm sure they didn't INTEND for their children to die. BUT they did intend to take the risk that their children COULD die because of the lifestyle they chose for themselves and their babies. They DID allow the circumstances that put their children at an extremely high risk.
Parents who punch and kicktheir kids, shake and toss their baby across the room, leave their little one in the locked hot car or a bathtub for "just 5 minutes", etc. probably didn't INTEND for their children to die either. But they're still responsible for the death of their children because any reasonably intelligent person knows that any of those actions can lead to death.
These horrible mothers allowed their children to be murdered, no ifs, ands, or buts. Maybe they didn't hold them up as shields, but that point doesn't matter because they still chose to put their babies at risk. HOW these babies died isn't the point either - they could have died because mommy left them in the car to make a quick drug deal, or because mommy left out the drug stash and baby decided to have a taste, or because they happened to be in the room when daddy's drug dealing competitors decided to drive by and shoot at the house, or because one of mommy and daddy's druggie criminal associates was visiting and decided to rape and strangle one of the babies while all the other adults were busy making deals and getting high. We hear about cases like this every day, there no reason to expect that people who actually live that sort of life didn't also hear or know of the risks.