I dont think they are lying. At least not intentionally. But the minute you suggest that civilization existed long ago and declined...it is going to ruffle some feathers.
Its the same thing where humanoids roamed the earth. And then, boom! they were farming and building cities, and writing stuff down.
Yeah...that’s evolution.
Any other explanation opens up too many doors answered by guys with messy hair suggesting “Aliens?”
Only primitive societies carve totem poles.
Not very good evidence of “alien” visitations, in my opinion