How did Harry know how Voldemort had lost his powers?

Question

At the end of The Chamber of Secrets Harry says:

“No one knows why you lost your powers when you attacked me,” said Harry abruptly. “I don’t know myself. But I know why you couldn’t kill me. Because my mother died to save me.”

If no one knew how Voldemort lost his powers as it can be written in the first chapter of the third book this:

Harry had escaped from the same attack with nothing more than a scar on his forehead, when Voldemort's curse, instead of killing him, had rebounded upon its originator.

Answer 1

Due to Lily's sacrifice of love, Voldemort's killing curse failed to affect Harry and instead rebounded on himself.

Had Voldemort died from the rebounding curse, there would be no mystery. The killing curse meant for baby Harry instead landed on the perpetrator and ended him, as expected.

The mystery is why Voldemort didn't die. Why was he left alive, having simply lost his powers, as opposed to completely dead, which would have made sense?

In 2004 (before Book 6 was released and we were introduced to Horcruxes), J.K. Rowling hinted at this:

We should be asking "Why didn't Voldemort die?" Not, "Why did Harry live?" but, "Why didn't Voldemort die?" The killing curse rebounded, so he should have died. Why didn't he? At the end of Goblet of Fire he says that one or more of the steps that he took enabled him to survive. You should be wondering what he did to make sure that he did not die — I will put it that way. I don't think that it is guessable. It may be — someone could guess it — but you should be asking yourself that question, particularly now that you know about the prophesy.

Answer 2

But if everyone knows that the curse has rebounded on Voldemort (causing his destruction and loss of powers) because Harry says:

No one knows why you lost your powers when you attacked me,

Even at the beginning of the second book it is written that no one knows the reason for the loss of Voldemort's powers:

“Harry’s parents had died in Voldemort’s attack, but Harry had escaped with his lightning scar, and somehow — nobody understood why — Voldemort’s powers had been destroyed the instant he had failed to kill Harry.”

only in the third is information about the rebound of the curse revealed to us:

Harry had escaped from the same attack with nothing more than a scar on his forehead, when Voldemort's curse, instead of killing him, had rebounded upon its originator.

For me this is a writing mistake. Because in the first two books no one knows how Voldemort loses his powers (Harry often says this) and suddenly in the third we are told that the curse has rebounded.