They had already revived Madara Uchiha using Impure World Reincarnation, but Madara in that state wasn't strong. He didn't have the power he'd possessed in his prime.
After learning that Sarutobi Hiruzen and the others had improved Impure World Reincarnation, Madara had immediately released the jutsu without hesitation and asked Obito Uchiha and the other man to revive him again.
Even if this modified Impure World Reincarnation could only last seven days.
Though he claimed not to care and acted dismissive, Madara didn't think Uchiha Brahman was some weakling or good-for-nothing. If he really were useless, he couldn't have subdued the entire Shinobi World and the Five Great Ninja Villages all by himself!
He'd crushed all resistance in a single day!
Now that Uchiha Brahman had command of the entire Shinobi World's power, Madara thought that without regaining the strength of his prime, he might not be a match for him.
To be honest, even Madara—a top Uchiha Clan fighter who had once possessed the Mangekyō Sharingan, the Eternal Mangekyo Sharingan, and even the Rinnegan—couldn't quite understand how Uchiha Brahman, a man with only a pair of Mangekyō Sharingan, had managed it.
How could he have subdued and crushed every village in the entire Shinobi World all by himself? It was simply unbelievable.
"There's no denying it: Uchiha Brahman is strong! Incredibly strong! At the Mangekyō stage, I can say that Uchiha Brahman is the strongest in the history of the Uchiha Clan!"
Madara had been revived. He stepped out of his coffin and spoke slowly in front of Obito Uchiha and Black Zetsu.
Black Zetsu and Obito looked at Madara, confused. Hadn't he said just a few days ago that he could easily suppress Uchiha Brahman?
"But! Against these eyes, against my overwhelming, invincible power, he still falls short!"