Sorry, but you're comparing apples to oranges like you're living in some sort of a bubble. Let me explain something to you. Professional combat sports are not organized like structured leagues in sports like basketball/soccer/football etc. In those sports due to massive audience and big organizations, you are absolutely guaranteed some money if you fulfill certain conditions like winning a league or a cup or advance to a certain stage of it. Also, TV rights are usually sols for the whole league so you get a cut of that too. So in those sports you can have the most boring and unappealing playstyle, but if at the end of the season you win, you get that money. You will still make WAY less money from sponsors than some teams who have more marketable stars or are playing in a way that's more appealing to your average fan.
There is no such thing in professional combat sports. Your audience is way smaller due to the violent nature of the sport and the PPV model, and these organizations are private companies that don't get financed by the state and massive machinery of big organizations like FIFA or some national league in soccer for example. You can't sell TV rights for much money, and that's not only because of the PPV model cause there are some "TV" events, but just because of the fact you don't have as much audience. So, in order for these private companies to even keep their lights on, they have to be a mix of sport and show business and that's why they are also unfair to a degree, because there is no clear rule on how one gets a title shot etc. and your average fan will fall for the "champ champ" bullshit, even though the guy who got the title shot often doesn't even have 1 fight in that division and it's very questionable whether he or she would have been able to actually get one in a fair way if that was mandatory.
In other words, in these combat sports 90+% of the time you're paid exactly as much as you are worth and you can't fucking expect to share the profits equally or even to raise the minimum contract etc., because the company would go under very, very fast. It's up to the fighters to promote themselves with their fights and personality. Most people buy the PPV cause of 1-2 fights, they don't care about some unknowns fighting. On some level it's unfair, of course. But they are your customers and you have to cater to them, if they pay to watch a certain fight, you can't pay fighters nobody cares about if they don't attract viewership. Ofc this is fucking brutal, but every single fighter knows how the business works before he or she gets into it, 90% or more of them will never ever make it and they're risking serious injuries and brain damage, but it's their choice to do this. If you're an "unknown" fighter and have a 3-4 fight contract, chances are you'll be on at least one or 2 decent cards and if you perform well there and perhaps get a bonus for KO of the night or whatever, not only will you make more money that very night, but people will recognize you and will want to see you again. It's up to the fighter and their manager to negotiate a good contract, that's just how the business works. Again, it's brutal and most of them will never make it, but that's life and they chose to do this.
Unions should exist for 9-5 jobs for jobs that are actually contributing to society in a meaningful way and which are required for everything around us to function properly. As much as I love MMA, at the end of the day it is only entertainment and a pretty mindless one at that, even though skill and effort are required. If all the boxers, MMA fighters and every other athlete in the world disappeared and got teleported to another planet tomorrow, the world would change but it would still function. If just 10-20% of nurses, garbage men or any type of laborers disappeared from a major city for 2 weeks, you'd have chaos. I understand the idea of a union for MMA, but these fighters and managers who want to make one should first try to run a MMA promotion and then see if they change their minds
. How on Earth can it be fair for some guy or a girl to get some sort of minimum decent contract if nobody knows of them and they are not attracting audience, and on the other hand fighters who invest in themselves, do all the promotion work, try to finish fights and get bonuses and attract more audience are getting a paycut just because of the ones nobody knows about? Again, this is not some socially productive work that's required for the society to function properly, it's mindless entertainment like most sports so this is where it's fair for capitalism to be 100% brutal and where they literally get paid what they're worth.
