>>115210139Anansi had chosen heirs for generation, but always with a pre-set destiny.
For his next pick, he wante his heir to have free agency, so the spider meant to transmit his power was irradiated by the machine, making a perfect mix of science and magic, allowing for the next heir to set its own destiny.
Once irradiate, it made its choice on Peter Parker, finding it the candidate with the most potential.
But peter would have kept using those powers for selfish reason, hadn't the death of his uncle happened.
everything I have said is canon.