The others were immediately confused as soon as they heard about the Vampire's Rise Apocalypse. They also had conversations with the members of their clan, discussing the Apocalypse Options they had been given. Most of them had only two or three options, and the Zombie Apocalypse seemed to be their best choice at the time.
After all, options like Demon Invasion, Ragnarok, or Dragon Awakening seemed far scarier at that time since they would not be fighting humans. On the other hand, they believed that the Zombies were manageable because they thought they would just be fighting against infected humans with slow movement and an obvious weakness: their brains.