It could also be that Fudge had some information about Harry's loved ones that he was using as blackmail or was about to use in a dangerous way. Harry, in a desperate attempt to protect his family and friends, might have resorted to killing Fudge to prevent that information from being misused.
Maybe Fudge was starting to turn against the wizarding community in more extreme ways. For example, if he was planning to persecute Muggle - borns more harshly or side with the Death Eaters secretly. Harry, being a defender of justice and equality in the wizarding world, would not tolerate such actions and might have been pushed to kill Fudge to stop his evil plans.
Well, in many fanfictions, Harry might use his quick thinking and knowledge of magic. For example, he could use spells in unexpected ways to get around Fudge's plans. Maybe he uses a charm to make Fudge misinterpret a situation or forget an important detail. Harry is known for his resourcefulness, and against Fudge, he could use his skills to expose Fudge's wrongdoings or prevent Fudge from interfering in things that Harry believes are right.
One possible motive could be a misunderstanding. Maybe Snape is framed for something really bad, like a dark magic plot against Hogwarts. Harry, in his haste to protect the school and his friends, believes Snape is guilty and takes drastic action. Another reason could be if Snape accidentally endangers someone Harry loves dearly, like Ginny or Ron, and Harry's emotions get the better of him in the heat of the moment.
It could also be related to the treatment of Harry's friends or allies. Suppose Fudge is persecuting Dumbledore or other Order of the Phoenix members. Harry, who is loyal to his friends and those fighting against the Dark Arts, would be enraged and yell at Fudge. He wouldn't stand for any harm coming to those he cares about, and Fudge's actions in this regard would surely provoke Harry's anger.
One possible reason could be copyright infringement. If the fanfiction uses too much of the original 'Harry Potter' material without permission, it might lead to a lawsuit. For example, if it uses the exact same characters in a way that goes against the original concept or if it borrows major plot elements directly.
Some would be shocked and horrified. Fudge was a well - known figure in the wizarding world, and his sudden death at Harry's hands would be a big shock. There would be those who would immediately condemn Harry, believing that there must have been a non - violent way to deal with Fudge.
Another motive might be related to a dark object influencing her. If Hermione came across a cursed object, like a dark locket that amplified negative emotions such as envy or fear, it could drive her to kill Harry. Maybe she started to envy Harry's fame and the special attention he always got, and the locket pushed her over the edge.
One possible motive could be that Snape is still deeply influenced by his loyalty to Voldemort in this fanfiction. Maybe Voldemort has some hold over him that forces him to do the unthinkable. Another reason could be a misunderstanding. Snape might believe that Harry has turned to the dark side or is about to, and he decides to take preemptive action to stop what he thinks will be a great evil.
One common theme is power and corruption. Fudge is often depicted as being power - hungry and making corrupt decisions in fanfiction, just like in the original books. For example, some stories show him using his position to suppress information or manipulate other characters for his own gain.
Perhaps in the fanfic, Snape discovers a powerful and dangerous magic that he wants to use for what he believes is the greater good, but Harry sees it as a threat. Harry has always been wary of Snape, and this new discovery could be the tipping point. Also, if Snape were to make a deal with a dark force in order to gain knowledge to defeat Voldemort but Harry misinterprets his intentions, it could lead to Harry killing Snape.
Well, in this fanfiction, Harry might finally stand up to Fudge in a really assertive way. Maybe he exposes all of Fudge's wrongdoings and incompetence in front of the whole wizarding community. For example, he could reveal how Fudge has been denying Voldemort's return and all the chaos that has ensued because of that denial.