Once when going up Gorgonio we stumbled across an abandoned campfire that had spread in some brush and a tree. Fortunately, there was no wind and we were able to put out all the fire except above 8' on the tree. Using a homemade roll-up J-pole antenna I was able to reach someone on the Laguna Peak repeater who relayed my message to the forest service who had no clue as to where I was talking about until I discovered they were in the Cleveland Nat'l Forest so I gave the Lat and Long and within an hour a helo landed with a hand crew to chain saw the then sparking tree down.
I wonder if the hikers were carrying a cell phone and it's hard to say why they couldn't limit its extent, maybe not be able to extinguish the deep embers but at least keep it from spreading. We used a combination of dirt, stomping and our water but if you've ever tried to put out a campfire then you know how much water is needed. Not having been there it's easy to second guess but I think I would have changed my plans to "babysit" the thing till help arrived. But then that is a bad place to be caught in a big fire so perhaps your life is more important and as C23 said
don't blame him at all for getting the heck out of dodge
From that second photo of the stump right next to the trail, it would be hard to believe it wasn't human caused
