Okay, I have to do this, this story is just that personal.
My Red John, the one with this backstory, is based partly on the Shadow Lord from the Deltora serieses (look up the books if you've never heard of them, they're AMAZING), Lord Voldemort, and…well…me. Yes, a lot of things about this Red John are basically self-insertion. I'm not a monster, but I don't really understand humans very much and "small talk" is repulsive in my opinion. I actually WISH I was as attached to human society as my Red John is - I'm bound by cultural conventions I myself resent and consider irrational. Some things about this Red John are qualities I have, and some are qualities I WISH I had. Yes, I want to be MORE like this Red John than I am. XD
More than anything else, though, I must give credit to my amazing parents, who are the Marshgoods to the letter. Yes, I was adopted at birth by an amazing couple who couldn't have children of their own, grew up as an only child, and have thrived on nothing but love and support from my adopted family all my life. We are also financially stable though not quite rich. Mom, if you're reading this, please understand, I don't want to do the things Red John does to his adopted parents in this story; the reason I gave him our (well, my) family is because I wanted my Red John to have NO REASON to be a monster, and you and dad are truly the best and most amazing parents in the world - the only way you could have raised anything but a wonderful person is if that person was innately and fundamentally inhuman and evil to begin with. I wanted to emphasize that my Red John CHOSE to be evil, with no reason whatsoever other than wanting to. I mean, that's what true evil IS - chosen. He's not hurting or jaded, there is nothing about him to pity or sympathize with - he's just a monster, a TRUE monster. Only with my upbringing could that be true of him - you and dad are just that awesome and I love you dearly.
And only as a true monster could Red John live up to the original hype that was created around the mysterious figure at the start of the actual show. That is what inspired this backstory, my entire series for which this is canon, and my other adjacent fanfics - I wanted to do justice to the villain as he was originally hyped up to be. I hope I succeeded; I have done my absolute best, and am so happy to share it all with the interwebs at last. Cheers, everyone. :)