She was trying to suck out everybody's life force with the machine she and her dumb sisters built, the Big-O'-Blaster. It was so she could fix up her ugly old skeleton of a body! [... Never mind that Kazooie and Banjo caused it to be a skeleton in the first place.]

She zapped King Singalong with it and stole his life force pretty early on... he would've been a zombie forever if we hadn't undone it.