If... if that was really the case, then a lot of things could be explained!
Maria Hill was now deep in thought. Umbrella Corporation and Hydra had originated from an ancient secret organization with a long history. They had merely split apart and become enemies because their ideals later diverged. There was nothing strange about that. It was like the Roman Orthodox and the Puritans—both believed in God, yet hadn't they later fought until they practically smashed each other's brains out?
They might have clashed several times throughout history. Perhaps traces of those battles could still be found, but lacking intelligence, there was no way to know the specific details. However, the recent conflict between these two organizations had most likely taken place within the Third Reich.
A formidable figure like Red Skull had suddenly emerged within Hydra and formed a new faction with extremely radical ideals. Umbrella Corporation had originally disagreed with Hydra's ideology, and Red Skull's faction was unorthodox even within Hydra itself. In Umbrella Corporation's eyes, that made them heretics among heretics!
Red Skull had hidden within the Third Reich, drawing nourishment and secretly building his strength, just as Hydra hid within S.H.I.E.L.D. today. Umbrella Corporation must have obtained intelligence about this as well, which was why they had infiltrated the Third Reich to stop him. That was how the rumors came about that Umbrella Corporation had close dealings with the Third Reich, or had even originated from it.
Judging from the final result, Umbrella Corporation's plan back then did not seem particularly successful. Red Skull had nearly flown a plane around the world and bombarded it with energy weapons powered by the Cosmic Cube. Yet their plan might also have been very successful, because afterward, Hydra was no longer a secret organization. It lost its mystery,