It's not that parents leave their kids in a hot car and just sit around all day going "hmm, I wonder where little Timmy is? Oh well!"
Usually hot car deaths happen because parents either completely forget their kids are in their backseats or because they somehow have a brain glitch where they think they dropped their kids off at daycare/preschool/school but didn't. So then they go their entire days assuming their kids are safe.
And that forgetfulness/brain glitch is usually caused by a combination of disruptions in their normal routines. Let's say the usual daycare drop-off parent is sick. The other parent is tasked with taking their kid to daycare that day, which is something they've never done or haven't done in a long time. The kid is tired that morning and unusually quiet in their car seat. The parent gets an urgent work call on their way to work and their mind completely switches gears from "must drop off child at daycare" to "must take care of this work issue."
So they completely bypass their kid's daycare and instead go straight to work. Their kid is passed out in their backseat not making a peep. The parent parks and hustles into their workplace just as they normally do and have normally done for years, because for that particular parent, taking their kid to daycare isn't part of their routine. And the urgent work call combined with the sleeping kid made them forget the change in routine.
They go into work and work 9 hours. Meanwhile, their kid died in a 130+ degree car while they were busy typing up emails and sitting in meetings. It sounds horrific and unthinkable but it's usually because of ONE lapse in memory and not due to an entire day's worth of neglect and forgetfulness.
I'm hyper sensitive to this because it's my worst fear for my son. I make my wife send me a picture of him when she drops him off at daycare on the three days per week that he attends. It's scary as fuck precisely because it often happens to parents who can't imagine how other parents can allow it to happen to their children.