I keep thinking about this in the back of my head. Trying to reframe it to be more empathetic to the family. They adopted him 3 years ago. Maybe a lot has changed in 3 years. Maybe the family is under incredibly tough times that they weren't 3 years ago and doesn't have a safety net or childcare lined up for whatever window of time is between job shifts. Texas doesn't have a minimum age to leave a child at home and maybe they recognize that it's not a great choice but if they're barely making ends meet, maybe there is no other option--it's leave kid home or lose job.
Maybe the dad was just dead tired after coming home from second shift, appreciative of the fact that it's night time, that there is some sort of solace in knowing "Troy's asleep in his room" and that he can just crash, no need to open the door and look in and potentially wake the kid up.
Or maybe this wasn't normal circumstances. Maybe dad had to work a double shift (so even more tired than normal) and just wasn't as mentally alert as he might normally be.
It's a tough time to be a parent, or just a human in general.
ETA: I want this to all be true but also acknowledging that the police have said in numerous places that they are treating it as a potential criminal investigation which, ugh.