He was an opportunist who played people. Basically a con man. Lying was part of the craft.
Assuming that the thing in the files is even legitimate. Those files are full of uncorroborated and bogus garbage that the FBI received as "evidence" but deemed false.
Something in the files does not immediately mean its real. It means the FBI gathered it up at some point. They can't throw away false info, it all goes "into the files." And now stupid people are claiming its all gospel truth.