Folks or folks of folks who failed background verification, how did it happen?

Folk of folks. Ex manager had used fake experience. We got new project , project had some work which required US Homeland Security Clearance or something . Whole team went for BGV again, some of us were 5-6 years tenured.
BGV ppl found out that managers first job was fake. Manager got termed, blacklisted On a shared database that all these bgv companies share. Last I heard, he was doing poultry farming