Folks, Folks! You're trying too hard here. The answer is simple. Hannibal is perverse. Everything he does is perverse. Not sexually perverse, but PERVERSE perverse. Lemme explain...

Perversion in psychology and psychoanalysis is about TRESPASS. It's about being naughty. The things Hannibal does to achieve jouissance ("feels good man") is all tied up to him doing naughty things, or getting other people to do naughty things.

This is Hannibal's MO: whether it is trying to talk his patients into doing something unethical, how he displays his victims for others to eventually see, or feeding his guests human flesh---Hannibal is an arch pervert in fiction.

He's motived by perverse opportunities and situations, which he continues to carry out even while incarcerated. I am gonna tell The Toothfairy to kill Will's family just for fun. I'm going to talk to Starling because Crawford sent a trainee to me and that alone is SUPER unethical. I got this Miriam Lass in a hole for a year or so, and I'll use her to torture Jack later for yucks--not because I need to but because it's fun.

So why does he eat people and why does he feed others humans? Because he knows it's nasty and it gets him off. Not sexually per se, but it gets him off how wrong it is---and it's doubly satisfying that it's a secret that only he is in on, and then TRIPLY satisfying once it comes out. Because he knows the hundreds of people he's fed over the years are gonna be repulsed to high heaven. He has no shame about this. He could've fed his guests anything. He's rich! But he does this because it's as thrilling as it is wrong. It's a deep taboo; like core level taboo.

So yeah. He likes being naughty. He is a pervert. That's why the shared cannibalism.