Well, in most such fanfictions, it could be due to his magic going out of control. Maybe a spell he cast accidentally interacted with the SCP containment systems in a way that disrupted their normal functions and led to the breach.
By simply looking at the facts. 'Harry Potter' was published years before SCP even existed. So it can't be a fanfiction of something that didn't exist yet.
The unique elements often include the blend of two very different universes. The magic system from Harry Potter and the abnormal, often terrifying entities from the SCP Foundation. For example, a Dementor could be compared to certain SCPs that drain life or emotions.
There would likely be chaos. SCPs are often dangerous and unpredictable entities. Their release could mean destruction of the surrounding areas, harm to innocent people, and a general breakdown of order.
No way. 'Harry Potter' has a very specific and well - crafted lore that is centered around the wizarding world, Hogwarts, and the fight against Voldemort. SCP fanfiction, on the other hand, has a very different and often very dark and subversive set of concepts that are not at all related to the charm and magic of 'Harry Potter'. The two cannot be related in the way the statement implies.
One interesting 'Harry Potter SCP Fanfiction' could be 'Harry Potter and the SCP Foundation'. It combines the magical world of Harry Potter with the strange and often dangerous entities of the SCP Foundation. In this fic, you might see how the wizards in the Harry Potter universe interact with SCP - related things, like dealing with some SCPs that have magical properties or how Hogwarts might be affected by the existence of SCPs.