All of this.
As long as a head or two is on a spike for the public to see, the systematic failures will continue to worsen and these things will continue to happen and the cycle will just keep repeating.
Mistakes will always be made where humans are concerned, it's unavoidable, however the mistakes and effects can be minimised with systems that are robust, that work, that have enough funding to work and be robust. We don't have that, we have a broken system we're expecting humans to hold together under more and more pressure with less and less resources. It doesn't work.
But the handler and/or the manager will be scapegoated for all the failures that led to this and people will have a name or face to blame and go back to their lives until the next time, and the time after that, and the one after that.
That's not to say the role of the call handler and manager shouldn't be looked at and the decisions questioned, but we need to see what a) led to the situation where someone caring for their profoundly disabled child had no support meaning an ambulance was their only chance of this being caught, especially after a physical illness requiring hospitalisation and b) what pressures are on the service when it's got to that point to influence the decision to close the call and not send the ambulance.
No good expecting a perfect service from individuals within a very broken framework.