“And for this reason God will send them strong delusion, that they should believe the lie, that they all may be condemned who did not believe the truth but had pleasure in unrighteousness.” ‭‭II Thessalonians‬ ‭2:11-12‬ ‭NKJV‬‬

I don’t think it’s a matter of intelligence as much as the desires of the heart. If the individual enjoys the evil aspects of life more than Truths, they won’t be able to see through the fog of their own sin. No matter how loud we think the train is, they have noise canceling headphones on by choice.