>>45359330Why do you think N didn't also beat the Gyms? His goal from the start was to beat the League, and we know he fought the Elite Four fair and square before beating Alder.
A Pokemon doesn't have to be raised to be strong, and a trainer doesn't have to raise Pokemon themselves to be a good battling pair either. Just look at any time the protag gets a gift or set encounters like legendary Pokemon, like when the XY trainer is just naturally gifted at Mega Evolution and stomps Korrina with a newly met Lucario.