It’s been ongoing for Nigerians for a long while now, it didn’t just start. Almost as if Nigerians have been blacklisted. Recent stats show that Nigeria is now the poverty capital of the world, which means that so many people may just want to use visitors visa to travel and never return. Over 5m people have lost their jobs in the last 3years so it is hard to have more people applying for visa now if they do no have money to spend and jobs to return to. So they see many applications as potential runaways. So many Nigerians depend on agents to prepare and fill out their application forms thereby most of them usually can’t collaborate the info they have on their form when asked during the interview.
Lastly, most consular officers are psychologists so they can read body languages well to know when people are not being truthful.