"Non si è mai saputo il perché."

[madmcmurphy]

And why is "It was never known why" incorrect?

[dnovinc]

I think it is because of determinative article "il" before perché. I can't give you a better explanation , maybe someone else will

[madmcmurphy]

Ok, thanks, I think I get it

[asa-tor]

Surely "It was never known why" would be a more accurate translation though, right?

[VincentJ]

I don't this so. "the why" is pretty common in French (I'm French) and it's probably the exact same one here.
I don't think madmcmurphy translation is wrong