How do you know they did nothing to prevent it happening? And that it wasn't just a tragic (unintentional) reality that RH failed to do so on that one day?
I also wonder (meant generally) why it is that peeps seem to believe RH at face value when what he says can be interpreted as damning, but disbelieve anything he says that can be interpreted as exculpatory?
The quote by him you include can be interpreted, imo, as his acknowledging he was aware that such deaths could happen- as in, he's telling LE he knew these deaths happened, and he found the very thought of it happening to Cooper "horrible," which made it all the more inexplicable to HIM that he could have been responsible for Cooper dying such a terrible death.
Few of us here (including me) seem to have any great understanding of FBS. Why would anyone expect RH to have that understanding, especially just hours after he found his baby dead and facing suspicious LE, when he was still on figuring out and explaining how he could have "forgotten" Cooper?