What causes a person to lie to the public?

Obviously, the first answer that comes to mind for most people is that a person lies to the public in an attempt to save face from something that has been shared and was never intended to be known to the public. Realistically, they do it because they panic and stop thinking at all. They'll make up a story and then tell you that no one knows how it was achievable, because the facts are it didn't happen, and so no evidence that exists will back the story shared...and that reason alone is actually why no one knows or is able to prove how it happened.
Even greater than that response, is the regularly occurring lack of gathered experiential awareness that this type of response never really gets picked up the way the Liar hopes. There will always be cracks in the story that cannot be filled with verifiable information, or alternate concurrent viewpoints, because the story itself is fiction.
So I beg forgiveness in failing to comprehend how anyone who has existed within the limits of this City for the last five years at minimum has not yet learned that the things they do in the "dark" will most definitely come to light, and the business you seek to keep to yourself is already out on the tongues and minds of your neighbors before you even assembled that story. And the longer you've been here, the sadder it is if you don't recall that this right here is the biggest little city you've ever lived in, and we are all over each other's business in ways the internet has stripped you of being able to hide.
These last 26 years have been on permanent record in the way you were lied to about your first 18. The internet is forever.
But also, paper trails still exist. Maybe they're easy to forget about because a digital trail doesn't hold the same depth of resonance that a pen on paper does, but it's still there. You still filled out forms, called officials, filed paperwork, posted on your social media stories, and all of this information exists on the World Wide Web for any curious researcher to track down and analyze. And when you provide the information yourself, you have no one to blame but yourself. So, maybe it would behoove more of us to come forth with the truth at the beginning?
Or maybe that's just not a quality of the human condition?

There is a great amount of viable information one can pick up from reading the way a caption is worded to scoping the background of a chosen photo. Whether or not you have the critical thinking to effectively note and analyze these details depends on your personal willingness to use your gray matter to begin with. It's a choice very few individuals make with any discerning regularity. Maybe you should work on that.