Depends on the lie.
This is a lie:
This is much closer to the truth:
So did the lie become truth? I think to say it didn’t, that it’s still a lie, completely misunderstands human nature. Humans whitewash over the ugly things in life. Sometimes those ugly things matter, sometimes they really don’t. Does it really matter what Jesus really looked like?
Jesus himself lost control of the narrative the second he died. When the Romans decided to craft a new myth around Jesus, they asserted a kind of ownership over it. This is the way history has always worked, we have to go and dig up the truth if we want to know it.
But it doesn’t make the new Roman myth any less salient and meaningful to people. Even though we can use simple logic to deduce what Jesus really looks like, most Western Christians are not going to have the second image in their minds when they pray. The lie is truth. Jesus of Nazareth looked like the second picture, Jesus Christ is pictured in the first.