* To intimidate Harry: Draco, being a pure-blood wizard from a wealthy and powerful family, saw Harry as an outsider and a threat to his social status. He wanted to establish dominance and make it clear that Harry wasn't welcome in his circle.
* To show off: Draco enjoyed flaunting his wealth and status, and Harry, being an orphan who had never been to Hogwarts, was the perfect target. By boasting about his family's connections and his own magical abilities, Draco was trying to impress his friends and intimidate Harry.
* To gauge Harry's strength: Draco, despite his arrogance, was also aware that Harry was special. He had heard rumors about Harry's survival of Voldemort's attack and wanted to see firsthand how powerful Harry really was.
* To make a connection: While their initial interactions were hostile, Draco was also drawn to Harry's fame and power. He saw an opportunity to forge a connection with someone who could potentially enhance his own standing.
Their encounter on the train set the stage for their ongoing rivalry throughout the series. Despite their differences, they eventually found themselves on the same side during the Battle of Hogwarts, demonstrating the complex and nuanced nature of their relationship.