Those lines were to stop the fire but this fire had some strange behavior and just kept crossing the lines. That said, they do start with fire lines further back and build additional ones closer to the fire so that if the closest lines are crossed there are already backup lines ready to go, so the closer lines aren't usually as fortified.Were those lines built knowing that the fire was going to go by them (maybe to slow it down?)?
I'm friends with several of the firefighters who worked the fire so here are some insights into what happened.
-More dead trees than usual this year increased "crowning," when the fire moves through the treetops and this crosses fire lines more easily than ground fires and sends embers further.
-The terrain, as you know, was extremely rough in many of the places so there was more roll out, when burning logs or rocks carrying embers are released as the ground level vegetation burns, sending them rolling downhill and igniting things along the way, often across fire lines. Much of this was caused by the Yucca in the particular fire, they started calling them "Yucca Bombs" or something like that.
-The terrain and heat also creates its own small weather patterns with extremely strong winds that push the fire in difficult to predict directions.
-Sometimes they ignite fire along the fire lines to burn toward the main fire and use up the fuel before it arrives. On at least two occasion for sure, and perhaps another that was unconfirmed, the back burns crossed the fire lines themselves and helped the fire progress.
-The rough terrain also often prevented fire lines from being completed as desired so they were still weak when the fire arrived, this was a major problem along the south bank of the kings river as it moved by the Boole Tree and towards Dunlap.
All of this together helped the fire cross more lines than many of the firefighters had ever seen in any other fire and gave it quite a reputation. They basically chalked it up to luck that the fire stopped where it did and didn't burn the Snowline Lodge and Dunlap, it was essentially a miracle aided by prevailing winds and some small changes in the weather. I guess that was probably a longer response than you wanted, sorry. It was quite the fire to watch and I'm glad it didn't get our cabin in Wilsonia! I actually have a collection of the briefing maps that I would get after the AM briefings from the southern command that I will post in the cabin and use to talk to my students about fire ecology.
Hope that helped a bit!
-Daniel