It was all just a hype.
It started out great. But along the way, there were a lot of illogical actions the characters did. Unnecessary sacrifices were made. Hugging in a place where you know is unsafe. The overall show was really lacking, compared to other korean zombie shows like Kingdom, Train to Busan, Peninsula, Alive. The show really is a far cry to all its peers. The show even mentions Train to Busan, and you could have thought that they would have an idea of what to do, they come up with a good idea and botch it themselves. When the class pres became a hybrid, one would think that she'd go outside and lure all the zombies with sound so the rest could escape, but no, apparently the smartest among them couldn't think of that. The people and the zombies almost have the same IQ.
If you're looking for a compelling story, this isn't it. Just bad story and direction. If you've watched any of the korean zombie movies, you'd be able to tell that this show was not really well thought out..