It could be due to some dark magic influence. There might be a spell or a dark force that made Harry act out of character. In the wizarding world, there are many instances where magic can cloud one's judgment and make them do things they wouldn't normally do. So this could be a factor in Harry throwing the Weasleys out.
Perhaps Harry has been through a very traumatic experience that has made him paranoid. This experience could have made him view everyone with suspicion, even the Weasleys who have been his friends. He might think that having them in his house poses a threat to his safety or the safety of others he cares about.
One possible reason could be a misunderstanding. Maybe Harry overheard something wrong about the Weasleys and in a fit of anger, threw them out. For example, if he thought they were plotting against him when in reality it was a big miscommunication.
One possibility is that Harry has been betrayed in some way by the Weasleys. Maybe he discovers they've been using him for their own gain, like getting access to his fame or fortune. So, in a fit of anger and disappointment, he throws them out.
In some cases, it could be that the magic system itself is the antagonist. For example, if there are ancient magical laws or curses that are affecting Harry's judgment and making him act against the Weasleys. The fanfic could then be about how they all fight against the constraints of this magic system to reconcile.
Well, it could severely damage their relationship. The Weasleys, who have been like family to Harry, would be deeply hurt. They might not be as quick to forgive him, and it could create a rift that lasts for a long time.
One possible reason could be a misunderstanding. Maybe some dark magic was involved that made Harry believe the Weasleys were acting against him or the wizarding world in a way that seemed illegal. For example, if there was a spell that distorted his perception of their actions.
Well, it could be that in this fanfiction, Snape is written in a way that endangers Harry's friends. Harry is very protective of his friends, so if Snape is portrayed as harming them in some way, Harry would likely try to destroy whatever it is that's causing the threat. Also, it could be related to some prophecy or hidden knowledge in the fanfiction that makes Harry believe Snape has to be stopped.
It might be due to a self - sacrificing decision on Harry's part. He could believe that by leaving, he would protect the Weasleys from the dark forces that are constantly after him. Since he has so many enemies, he might think that as long as he is around the Weasleys, they are in danger.
One possible reason could be that Harry is preoccupied with his own dark thoughts or problems. Maybe he's worried about Voldemort and his plans, and in his distracted state, he unconsciously ignores Mrs. Weasley's attempts to reach out. Another reason might be that he's trying to be independent. After years of being in the wizarding world on his own terms, he might not want to be mothered too much by Mrs. Weasley.
One possible reason could be extreme self - sacrifice. Maybe he believes that by stabbing himself, he can save his friends or defeat Voldemort in a very unique way. For example, if there is a dark magic spell that can only be broken by his own life force.
Perhaps Draco has developed a sense of respect for Harry over time. He might have seen Harry's courage and determination up close and decided that Harry is worthy of his help. Throwing the wand could be his way of showing that he acknowledges Harry's importance in the fight against the common enemy.
One possible reason could be that Snape suspects Harry of something dangerous or against the school rules. Maybe he thinks Harry is involved in some secret Dark Arts activities and ties him up to prevent him from causing further trouble or escaping while he investigates.