AgathaCreepypasta
The wizarding world was blind to who Albus Dumbledore really was. They believed he was a saint, they believed he could do no wrong. They considered him and his Order as Wizards and Witches of nothing but light and love.
He told everyone the story of the Boy-Who-Lived, made sure that everyone saw the boy as a savior, and then planned to groom the child to sacrifice themselves and defeat Voldemort for good. So that Albus Dumbledore could step up and take the fame and glory once more.
He did not anticipate the events that occurred before the "victory" of the first war. In contrary he had never known that hey happened, he had overlooked a crucial detail that was going to lead him to his downfall.
This is how Harriet Lilly Potter was going to bring down the man that caused her so much pain, that caused the loss of her mother, the loss of her voice. And when Voldemort found out what had really happened that night. He was furious, and determined to get his body, power, and all pieces of his soul back. He was determined to find and protect the child.