It's a corner they wrote themselves intoWell.... They got caught in a corner....
They don't want to make Vecna look weak. They didn't want to kill Nancy and not give Vecna another L. It's pretty simple.... They had to make a convulted way to make it out without doing those thing. So, he told Nancy to bring Eleven.... Which doesn't even make the slightest sense. 99% won't even notice it. Also... she wasn't the final victim. It was always max