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human
[General fantasy/horror] Why do so many people worship openly evil gods?

To be clear, I know that there are evil gods who lie and pretend to be good, or have cultists pretending they're good. That's fine, people get tricked.  


But there are also lots of fiction that have evil (or at least, destructive and hostile) gods who openly and outright show up and say they're evil, but still get large churches.   


D&D has self-proclaimed Gods Of Evil who use titles like The God Of Tyranny and The God Of Slaughter. HP Lovecraft has  loyal worshipers of the Great Old Ones who are fully aware their gods are amoral alien monsters will kill them and never notice. Christian Fiction has entire conspiracies of Satanists who know Satan is an evil demon who will drag them to hell to suffer forever and seem totally down with that. World of Darkness has followers of the Wyrm who put huge effort into making the earth an uninhabitable polluted wasteland. Khorne from Warhammer leads with "I'm the murder god and I want indiscriminate murder".  
There are countless other examples among fiction-  the Apokolipsians ,Mehrunes Dagon and Molag Bal, the First Evil's harbringers...

I can see the odd misanthrope or sociopath siding with them, but large cults? Outright religions? National churches?

Why are so many people pledging allegiance to evil abominations who openly want to hurt everyone, including the faithful? What do you get out of worshiping the God Of Betrayal, Deceit and Cruelty? How do they think this is going to end?
gpt
Some followers believe they will receive power or favors for supporting the evil deity in their attempt to rule over everything. Others believe that they will be spared (and/or reborn/recreated) when the evil deity fulfills its desire to destroy the universe (especially if said deity wishes to create a new universe after the destruction of the original), filling such a new universe with its followers.

And then you've got the groups of nihilists and misanthropes who just desire destruction and oblivion.