Sometimes the best fighters come from the more difficult starting points. The hunger for success.
Mostly not I think. Conor, Arnold Allen, Ilia, Poirier, BJ...all examples I can think of where they had parents, a bro or partner to rely on. Less likely to train high volume if you've got rent to pay. With the financial help you can be choosey about what work to take, if any at all. Less missing sessions or having to get home from training at near midnight, shower, eat and then wake up for work at 5:30 (which I've done many times). That's why I rate Gomi even more highly after learning he was disowned by his father as a teenager. Or why I find young guys who sit at home with their parents smoking cigs and eating takeout and then say they can't afford to train, to be irritating.
End of the day hunger becomes irrelevant if someone can't get into the gym and get the quality volume in. Hunger doesn't win fights, training does.
Best base is going to be passion/hunger (which can come from hardship), combined with practical opportunity.
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As for the question idk why training a few hours a day 6x a week isn't believable. "Hard" is relative, but it's largely skill work and is very recoverable if they have good fitness and are careful in some ways (eg don't have poor posture, warm up, don't keep doing things that cause bad types of pain). If people can work physical jobs and then train too, I don't see how it's not doable. The human body can adapt to a lot if it's gradual and then consistent. It's like doing a new physical job 2x a week and thinking fuck this is hard, but later you can do 6x a week. Actually I think it's actually easier to do more, because your body gets adapted to whatever you do...I found training harder when working in offices than when more physically active throughout the day. As long as a physical job isn't literally injuring you eg fking up your fingers. I find 2x a day 4 times a week pretty easy (assuming sleeping half-adequately), can still do extra pushups, pullups and/or solo drilling at the end, plus running a mile to the gym and easy jogging hills once a week (finishing with around 15 broad jumps) and some prehab at home a few days a week. I'm 100% sure my body can adapt to more volume and intensity, if built up conservatively and turned into habit.
Non-mma, I've seen on youtube a Korean high school where the judoka 2x a day 5 times a week. My old judo coach (a recent Olympian at the time) was devising a timetable and it was similar. Couple sessions a day, plus a few S&C per week, like front squats, split squats, plyometrics (depending on S&C level). I can't remember exactly.
Then some sports I believe the high level does WAY less training compared to MMA. Say field hockey in England (amateur sport here). 2x sport training a week, a competitive match at the weekend and running of some kind a few days a week. Many don't lift weights or maybe 2-3x/week. My dad coached at a strong level and this is the impression I have and I've seen it mirrored in research papers. However it'll depend vary between countries too, like some countries do more strength work, some countries are more likely to have dedicated S&C coaches at clubs rather than the general coach running everything, some countries have pro leagues. Probably some difference between in-season and off-season.
If you search online you can find training the old training logs of Seb Coe for middle-distance running, for the couple weeks before he set some records - can't remember if it was reflective of his year-round training. He ran 2x a day most days, one easy run, one fast session. Zapotek is another runner you can find info for.
