The premise makes the assumption that Satan is real. Besides, what is he lying about? Astronomy? Biology? Witch hunts? God? Other God's? Human history? I don't get how that question helps understand anything.
"We live in the age of the internet, and there are still people willing to blow themselves up for the HIGHLY UNLIKELY possiblility of pussy in another dimension!" - Joe Rogan
"Jesus Christ! Grab the Escalade, we're outta here!" - God
"Jesus Christ! Grab the Escalade, we're outta here!" - God