I think they just did not find this guy guilty because it would have a big negative impact on the firefighters and the Fire Soldiers. Therefore, then the good old, now widespread thesis of "mentally ill man" is chosen.
Unfortunately it is the same here in Germany and some other European Countrys. So-called migrants murder people here too, especially locals, and are not found guilty after that, although it's more than obvious that these people did it with full awareness or in the case of Muslims they did it because their "honor as a man" was soiled. Or it's just a misogynistic motive. Or they found it funny. ( like this Guy did obviusly)