TADC "Intolerable Knowledge" theory
Assuming SOMA - they are digital copies. This is the "intolerable knowledge" that they have to accept somehow, or else abstract.
Kinger knows they're all copies, and Jax has figured it out or strongly suspects it. Ragatha may also suspect.
If Abstraction is a mental breakdown, a major trigger could be the intolerable realization of being a copy, especially if it's sudden, with no chance to process or integrate that knowledge.
Integrating The Intolerable Knowledge
Kinger would never tell someone point blank they're copies, because he's seen it break people in the past.
Instead, Kinger offers emotional support and friendship - when he can. He has to avoid breaking too - he's also been through extreme grief and isolation. His survival mechanism is to simply not remember his situation most of the time. He can tolerate lucidity for short times, especially if there is a goal of helping someone else. He hopes to help people strengthen their minds and heal before the inevitable realization.
Jax's survival mechanism is to not count anything as "real," or counting as mattering, since none of them are "real." He avoids emotional turmoil through his own style of hedonism. He's not receptive to Kinger's character-building assistance, "because he's a coward." So, he is failing to work through trauma and build the mental resilience needed to live with the intolerable knowledge.
I imagine Jax was friends in real life with Kaufmo and Ribbit, and they might've all entered the Circus together.
Jax could've made the mistake of telling Kaufmo and Ribbit they are copies. Maybe he was sick of Kaufmo's exit obsession, or wanted to relieve him of it. But it backfired, and whatever Jax said or showed them was too much too soon for them.
He may feel responsible for that, that's why Ragatha's "not anymore" comment cut so deep. No friends left in or outside the circus.
In They All Get Guns, Jax carefully tries to explain his philosophy to Pomni, focusing on letting go of the attachment to who you used to be, without mentioning being a copy. He just focused on emotions: attachments just cause grief and misery, so embrace the fun things you can do now as a cartoon.
Jax is emotionally immature, but also seems perceptive and clever. He questioned Abel's claims intelligently. His archetype philosophy had a lot of thought put into it. He wonders about Gangle being capable of happiness - he probably thinks seriously a lot, but just rarely shares it. Because sharing his genuine thoughts backfired so horribly in the past.
He is perceptive enough to figure out the copy situation, before he was truly emotionally ready to know it. He thinks he has integrated the knowledge successfully, but he still has unhealed trauma, and could still abstract, because he won't do the work of healing and become truly mentally resilient.
Bonding with Pomni, then fighting
Jax wants friends who also see the truth, whose mental stability he doesn't have to tiptoe around (ironically), who he can just have fun with. Having others truly in the same boat, knowing the truth as he does, would help make this existence feel okay.
So, he carefully introduced to Pomni the idea of letting go, as letting loose, and Pomni reacted well. She had fun with him, and she gained confidence in her imaginative powers.
But then, Jax was reminded of his real life friends who abstracted. He remembered his connection to the real world. The thing that is dangerous to think about, to miss. To long for a time before all this. And that triggered the mental intolerability that lead to the fight, and that eventually leads to abstraction.
Or, he might have thought Pomni is already resilient and truth seeking, maybe she could actually handle a nudge toward the truth, unlike others. But after the Kaufmo/Ribbit reminder, became afraid he might just be nudging her toward abstraction too, so he tried to burn that dangerous bridge, feeling like he doesn't deserve a real friend, out of guilt.
Jax's coping mechanism is ripping at the seams, the intolerable knowledge "knocking" in his mind.
Facing identity collapse, he may feel psychologically cornered, and in a crisis, be desperate to regain control. To relieve years of feeling powerless, he might put his advanced conjuring abilities to the test, designing an environment where he cannot be hurt, not caring how it affects others. Do unto others before they do unto you.
But just like everyone else, he'll have to heal and integrate the reality of their situation to avoid abstracting. Hopefully, they'll all help each other heal, integrate, and develop conjuring skills and create a beautiful new digital world together. I imagine Pomni leading this, even though she longed to leave and wanted to believe Abel so badly, she is the most mentally flexible and resilient, and is a natural leader.
"Ego death" can mean letting go of maladaptive self images that hinder growth. By rebuilding healthy identities, they can connect genuinely and meaningfully without risking abstraction anymore. Rebuilding character is the key to easing the longing, destructive attachment to the past.
Escape A Different Way...
I also think it'd be cool if they at least found a way to escape the computer they're on, to travel the seas of the internet, and at least escape the circus.
Especially if they could affect the world- not like they could before as physical humans, but from behind the screens, maybe even to help their real world selves. Tweaking algorithms to make the messages or articles they need appear right when they need it. Healing resources for Ragatha. Get Gangle's art to appear in the feed of a good connection. Delete Pomni's student loans. It could be a fun continuation!