It's difficult to get people to understand when they are wrong in their philosophy, and to change that philosophy especially if they're grounded into it for soil long a period.
We can look at Paul the Apostle. As an example, it took Jesus knocking him off his horse and blinding him for a few days to get Paul to understand the truth. And in some ways it'll take many of these who walk in darkness the very same thing, for God's intervention even though the word is right in front of them
Even for Paul, who knew the scripture inside out, he was a Pharisee. And he still didn't understand the scripture.