Maybe it’s not. What makes you think he hasn’t apologized to his victims?
As an aside, my wife has been saying for years that she felt Jana Duggar (the oldest girl) was the victim of sexual abuse. Now it turns out that she may be the only one who wasn't. In any case, I don't think the Devil just showed up at Josh's doorstep one day and forced him to molest his sisters. I think the whole lifestyle - the unsanitary long hair on the women, the forced long skirt wearing, and the really weird, controlling courtship rules gave the kids a perverted view of sexuality, i.e. the Duggars very lifestyle invited the Devil into their home.