Orochimaru looked at the instructions left by Tobirama on how to perform his ultimate masterpiece, and he skipped to the end of the scroll. There, in red, glowing ink and underlined several times, was one final warning.

"Do not attempt to summon an Uchiha with this jutsu," Tobirama had written, a sense of urgency clear even through the old and worn script, "they'll pull some sort of new power out of their ass to wrestle control from you and trust me, you don't want to be responsible for being the one who brought the eternal whiner to life."

Orochimaru chuckled as he thought of ways he could screw with future generations, and then ripped the part with the warning off the scroll of seals, ensuring that none would receive the warning about summoning Zombie Uchiha. Petty joy coursed through Orochimaru's veins.

Years later, Kabuto looked at one of the scrolls his master had left him after his untimely death. "Edo Tensei? I can use this..."

And that's why Kabuto was stupid enough to summon not one but TWO Uchiha with Edo Tensei.