Well he was one of the smartest persons in history, but not in any practical sense that would enhance the life of Average Man.
As for fearmongering, the first law in the official Handbook of Effective Fearmongering is to make any forecast, estimate or extrapolation as far into the future as possible.
E.G., don't ever say the sun will go supernova and explode in ten thousand billion years; be modest and simply say 997,000.52877 billion years.
Successful fearmongring demands that there is never the remotes possibility that anyone who is alive will never be able to confirm or deny the claim.
Just make sure that the claim is in the future a minimum of 200% of the oldest confirmed human in existence.
“Well he was one of the smartest persons in history,
And yet failed to know God, proving mental intelligence isn’t the totality of wisdom.