When it comes to extinguishing fire, you play the cards you have to mitigate the situation. If what you have is a residential fire hydrant system that can supply 36,000 gallons, you use water in overwhelming force. As evidenced by the article, it will not quell the reaction but it will dampen the overall thermal situation enough to permit humans to be extracted safely.

Presumably it would have been better to dump a few thousand pounds of sand on it but there are few sand hydrants in USA residential neighborhoods.