Well, there's also something called professional courtesy. Competition is nice and all, but it doesn't mean that they have to be at each others' throat.
Also, there is somewhat a camaraderie among creatives. Its somewhat hard to explain, unless you have been working with or surrounded by creative people, but they have a somewhat unwritten code that they don't meddle with each others' affairs or some sort. I mean if you trap a marvel artist inside a room with a dc artist with beer, they will be drinking together complaining about their own employers rather than criticizing each other. If they criticize each other, its usually in light-hearted mood or in jest, just like niggers calling each others niggers. Of course there are sometimes real fights, but most of that happens because of money.
The only creative people that goes against that are usually assholes and disrupters or idiots. You know, "that guy"
That's not true. The camaraderie you're describing is easy to understand, because it's natural state of any group of people with shared experience. Be it military, construction workers, stay at home moms or comic book artist. If you are generally leveled out basic human being, you will get that in a group setting- I have my own company and I will do a lot to get a contract over my competitor, but at the same time I will be first to let them know about any changes that impact our profession, because we are actually good colleagues who met through work. I don't want him to fail, but I do want to get better contracts.
Being competitive in that setting isn't wrong. My competition makes my work more interesting and drives me to offer something better and with that comes price increase for me and my competition, because we offer better quality and there are people who appreciate it over stuff new people can offer and cycle continues. This is how senior partner in law firm can ask for 600/hr.
We're not talking about cutting throats here, but the desire to be more successful by the virtue of being better.
The issue at hand is- these people don't want other people getting better, because I think they know they have nothing special to offer. No real drive or skills, no sales number, nothing the would make a publisher actully pick them over competition.
Read Ian Fleming's James Bond, Marvel's Fearless or any of Liana Kanga's shit this is prime example of a product with no competition. It's shit.
ETA: re read your post and it looks like you haven't actually worked with creative people and only read about it on twitter. Creative people are like any other people, just creative. There's nothing special about it and there's no such code in real life, only on twitter. When you go to school for creative stuff, you are put through a mental wri ger with amount of criticism you are getting there, everyone does that, your peers are required through project showings to tell you what's wrong with your stuff and profs do that every single consultation. At the end of this you understand that you're better of by asking for second opinion, leart to not take any of it personally and make your own judgements if the criticism was useful or helpul. You learn to be a better creative person and use criticism as a tool to improve upon your work. The situation you descrobe is absolutely undesirable and none of those special snoflakes could survive proper art school. (And they likely didn't, because art schools in US are a scam).