Well, perhaps the author thought that facing a dragon was an insurmountable challenge for Harry. Dragons in the Potterverse are extremely dangerous creatures. Maybe Harry underestimated the dragon's power or was caught off - guard in a moment of vulnerability, leading to his death.
In this fanfiction, the author might have wanted to explore a darker and more tragic ending for Harry. By having him die facing the dragon, it could be a way to show that even the greatest heroes can fall. It could be that the dragon represented a force of chaos and destruction that Harry simply couldn't overcome this time. For example, the dragon could have had some special abilities or was under the control of a powerful dark wizard, which made it impossible for Harry to defeat it.
One possible justification in the fanfiction could be that Harry was alone when facing the dragon. In the original series, Harry often had the support of his friends. But in this scenario, if he was isolated, his chances of survival against a dragon would be significantly reduced. Also, the dragon might have been in a particularly aggressive state, perhaps enraged by some dark magic. Harry, being only human, despite his magical abilities, might have made a mistake in his strategy against the dragon that cost him his life.
Well, it could be that the author made the dragon extremely powerful. Maybe it had some unique abilities or was of a super - rare and dangerous species that was too much for Harry to handle. For example, it might have had impenetrable scales and a fire so hot it could break through any magical shield Harry could conjure.
The author could also have set up a situation where Harry was alone and without his usual support. For example, his friends were incapacitated or separated from him. In this vulnerable state, the troll was able to overpower him. In the fanfiction world, this kind of isolation can often lead to a character's downfall, especially when facing a dangerous adversary like a troll.
Maybe it was a misjudgment on Harry's part. He could have been overconfident and thought he could easily handle the dragon on his own.
Maybe in this fanfiction, some dark magic forces manipulated the situation. They could have lured Harry Potter into a dragon - infested area and set up some powerful spells that prevented him from escaping, thus forcing him to face the dragon which ultimately killed him.
It could be that the dragon was an egg he found by accident. He, being curious and having a soft spot for magical creatures, took the egg and hatched it, thus becoming the owner of the dragon. In the wizarding world, there are often unclaimed or lost magical items and creatures, and Harry might have just stumbled upon this dragon egg.
I'm not sure who specifically created this fanfiction. There are so many Harry Potter fans out there creating various fanfictions, and it's hard to pinpoint the author without more information.
His friends would be devastated. Hermione, for instance, would likely feel a great sense of guilt. She might think she could have done more to prevent it. Ron would be angry and grief - stricken at the same time. They would have to reevaluate their lives and their fight against the dark forces without Harry.
In Harry Potter fanfiction, death can be protective in a rather complex way. Sometimes, when a character dies, it sets off a chain of events that ultimately protect Harry. Consider a situation where a wizard close to Harry is killed by Voldemort. This could lead to an outpouring of support from the wizarding community for Harry, making it harder for Voldemort to target him directly. Additionally, the death of certain magical creatures might release powers or magic that then shields Harry. For example, if a phoenix dies, its final burst of magic could be diverted to protect Harry, given the strong connection phoenixes have with the concept of protection in the Potterverse.
In many fanfictions, Harry might use his powerful spells like the Stunning Spell or the Killing Curse if the story allows for such dark magic use. He could also use his intelligence to outwit the dragon, perhaps finding a weakness in its armor or behavior pattern and then using a well - timed spell to defeat it.
The relationships that Harry was supposed to form later in life, like his friendships with Ron and Hermione, would never happen. And the whole wizarding world would be different. Without Harry, there might not be someone to stand up to Voldemort in the same way. So, the power balance in the wizarding world would be completely shifted. Also, the mystery around Harry's scar and his connection to Voldemort would be left unresolved in a way that leaves the story with a sense of incompleteness.