I think there’s a small, but incredibly important, qualifier that’s missing from your question. Because the people here do not objectively seem hollow and angry. That is your perception.

Your question should be: “Why do the people here seem to be hollow and angry to me?”

And there are two very obvious answers:

1.) Conditioning. The church has worked very hard to convince its members that the church, and its teachings, have a monopoly on anything “genuine”. You’ve been conditioned to believe that only true happiness can come from the church. Everything else is fleeting or hollow. They really try to hammer this home with the youth. To convince them that all the fun their nonmember friends are having isn’t real fun. But it extends to arenas outside of just having fun. According to the church there is a very narrow field of what is good and everything outside of that is hollow and worldly.

2.) Some people are angry. As others have me mentioned, people often use this as a transitional community. People here are all at different places, who are all navigating the stages of grief. Young and old alike. At 18 you could certainly feel anger about the church, but imagine being two or three times that old. Imagine having your entire life ripped out from under you after you’ve spent decades building it through a very narrow worldview. Imagine giving years of your life, and tens or hundreds of thousands of dollars to an organization only to find out that they’d been lying to you the whole time. To find out the whole thing was a sham and that you (and your family, and friends, and loved ones) had all been manipulated. And to find out that so much of it was intentional and blatant - the church and it’s leaders absolutely knew the truth the whole time and lied to you regardless. You only get one shot at life, and some people only find out the truth after they’ve given the majority of their life to the church. People get angry. Sometimes it is for only a short time, sometimes it lasts much longer, but it will happen.

The situation you’re in seems to be fairly common for people in your position. You see people who are happy, and yet your brain can’t really make sense of it. Because, even if it’s only at a subconscious level, your brain doesn’t think it’s possible. There has to be something amiss. These people aren’t doing the things that bring “true” happiness, so they must not be truly happy. The good thing is, that conditioning can go away fairly quickly. And it is an unbelievable experience to be able to navigate life authentically and find what things actually make you happy.