>>18605864He was probably a strong trainer in a time where Leagues didn't exist yet, then retired to become a Pokemon researcher once he grew bored of all of his constant victories. Even so, since Oak and Agatha were rivals, and Agatha herself is only the 3rd member of the Elite Four, I can't imagine Oak being that much ahead of her or behind, either he's Elite Four 2nd/3rd(Agatha) or Lance tier, and Red beat all of those tiers anyway.
Of course all that is just head canon.
