This was written by one of the people who lived at the time of Jesus. Not only that,
but he walked with Jesus,
traveled together with him,
ate with him,
was rebuked by him,
was blessed by him,
walked on water with him,
and shared a morning breakfast with him and some of the other disciples after Jesus was raised from the dead.
Peter writes this letter to those who are "aliens" and who are "chosen." This is the view from inside the tabernacle. Do you love me? (essay by J. C. Ryle) "The question which heads this message was addressed by Christ to the apostle Peter. A more important question could not be asked."