Why are people in dual spires so weird??

I just watched this episodes and it is one of my favorite episodes.... But I couldn't help but notice one thing. Why the hell is everyone is fucking weird, like I noticed throughout the episode something was wrong but in the end what the hell was happening. What's the reason behind this? Is it years of no social interaction with other people outside of their village and lack of technology or an even more logical theory.... Years of inbreeding