??? Doffy was THE epitome of a Celestial Dragon: spoiled brat, demanded slaves, insinuated that everyone around him was inferior. He wasn't born evil, every Celestial Dragon of his generation acted the same way like Roswald.
Doffy was found and nurtured by Trebol. Rocinante was taken in by Sengoku who raised him. One became a man who desired to sacrifice Law for his own ambition, the other became a man who loved Law and wanted him free. This is the same 100% nurture vs nature.
The only reason why Doffy rose as high as he did was because of his Conqueror's will. Of course it's going to make Cora think Doffy was special. That's how all Conquerors are just like Shanks.