What has happened to the rule of law in England?

The family were clearly well known to Social care. So likely that the kids have additional needs or behavioural issues. There seems to be a lack of engagement from the family with services trying to help them.

It doesn't specify the age of the children or their level of understanding, and infers they would not be capable of taking part in a purposeful interview, given social services didn't support them being interviewed.

Would you want them to go through it so you can point a finger? It doesn't even make clear if any of the other children were over the age of criminal responsibility.

From what is shared it seems it was accepted the overall culpability was on parents failure to supervise

Maybe they were under the age of criminal responsibility or disabled and not considered responsible.

The rule of law very much still applies.

What has happened here is that the parents have refused further intervention, and from reading between the lines I would bet the proverbial farm that this family is already known to SS due to previous incidents and at least one of the children has some kind of additional needs.

This is not the first fire that happened in that house. Six months previously "another member of the family" had set fire to a bed. The parents refused additional safety measures then.

From the article they are saying it was one of the other children who started that fire and the previous fire when the victim was asleep.