Salazar Slytherin created the Chamber not for the reasons most wizards and witches think
Everyone believes that Slytherin created the Chamber of Secrets because he hated Muggleborns and wanted to get rid of them, but what if it wasn’t like that? The text says that he merely found them untrustworthy but it never used the word ‘hate’ to describe his feelings toward them. So what if he created the Chamber not to kill but simply to protect the school. Since Hogwarts was founded during a time when magical people were still being persecuted by muggles and the school was a place of safety and sanctuary for wizards and witches. Slytherin might have thought that muggleborns were more easy to be corrupted by muggles themselves and possibly reveal the school’s location and secrets and the creation of the Chamber was a backup plan in case that ever happened. Not to mention you need to be able to control the Basilisk, it doesn’t just automatically kill or hurt on its own. Snape was testing Harry during the Duelling Club
Snape whispers something in Draco’s ear and not long afterward, Draco produces a snake at Harry. What if Snape whispered to Draco to use that spell, and was seeing if Harry was similar to Voldemort. He wanted to know if Harry could be a potential threat after Voldemort tried to kill him as a baby.- Or maybe Snape wanted to see if Harry really had Horcrux in him.
Newt Scamander gave Hagrid Aragog when he was small
Aragog says that when he came to Hagrid still an egg, he was in the pocket of a traveler who had gone distant lands…… well Newt was known to travel distant lands. And he sometimes liked to keep his creatures in his pockets. Draco knows Crabbe and Goyle are Harry and Ron in disguise under Polyjuice Potion.
Draco isn’t stupid, and Harry and Ron make several slip-ups when disguised as his buddies. He also should be able to sense if there’s something off about two kids he’s known for a long time—particularly ones this dumb and predictable. (In the movie Harry and Ron also retain their natural voices, though I’ll choose to discount that detail as it isn’t in the book.) This helps make sense of the conversation, as a lot of what Draco says has an As You Know quality about it; it’s not something you’d expect him to say casually. He’s probably saying only what he wants Harry and Ron to hear.The Basilisk wasn't a weapon originally.
It was a teacher left by Salazar Slytherin to impart dark magical secrets and knowledge to a successor to him ideologically if not by blood. Grant it was a particularly bloodthirsty monstrous teacher but it was intelligent, capable of living for thousands of years, extremely loyal, and one that could accurately judge a prospective successor to Salazar Slytherin's ideology. And the Basilisk taught Tom Riddle many dark magical secrets before he set it loose on the school setting him on the path to become a dark lord.