Why is beef butchered in small scale almost subsistence farming so tough that even tenderloin is only good for ground beef?

I just bought a whole beef tenderloin on a wet market in a small rural place in a developing country in Asia. I noticed something is wrong with it regarding tenderness from the first moment I touched it with a knife. It felt tough, way too tough. I only know its a tenderloin because I bought it whole, and it looks like a tenderloin, though its quite big (3 kg). I've cut a steak from it, and tried searing it on hot butter for a minute or two, very rare. I've cut a piece, and when I put it in my mouth, its like the toughest cut of beef. Its so tough, its not even edible in any other way then grinding. I tried cutting more steaks and cooking them a bit longer, on less and more heat, and the results are even worse. Had to make a stew out of it in the end. I am very surprised a tenderloin can even be so tough, I thought no matter how bad the cow is, you can make a somewhat edible steak out of a tenderloin. I was wrong.

My question is what causes it to be so tough?

Was it something in the way the beef was raised? It's a very small rural place, here they butcher about one cow a week usually, and they come from the local population where it is common for a family to keep a single cow, and slaughter it after a year or two, take some meat for themselves and offer the surplus for sale.

Cows are probably 100% grass-fed, or rather fed whatever the cow can find roaming around the village. People are very poor and they don't feed them grains, cereals even if they would want to, because they can't afford to buy any feed.

Is it about the way its butchered? Butchering process is very basic, no stunning, they just cut the throat of a fully conscious animal. There is no ageing of any kind, no hanging for a few days, as there are no facilities for that. There is even no refrigeration available. Cows are butchered around 2-3 AM, and the surplus meat is sold at 6-8 AM the same day.

Surprisingly, the tenderloin is not more expensive then other cuts of the cow, which means it's likely not in very high demand. The price the same for almost any cut of beef, equivalent to about 6 USD/kg (3 USD/lb). Interestingly price for beef shank with bone is 5 USD/kg, so the tenderloin is only 20% more expensive then the shank. Most local people who buy the beef from this rural source, probably don't even know what a steak is or own a pan. For them 1 kilo of beef is 1 kilo of beef, doesn't matter much which cut. They usually just put it all in a stockpot anyway, it makes no difference if its tenderloin or shank - this is my impression from talking to the local population.

In the same country, a tenderloin from a big city supermarket (where beef comes from completely different sources, more large scale commercial operations and professional abattoirs), is tender as any tenderloin normally is, and costs about 20 USD/kg.

This is not the first time I experience unusually tough beef from very-small scale farmers. A few years back I was living in a developing country in Eastern Europe and several times got into a cow-share buying part of a cow butchered in a similarly basic operations, outside of the normal commercial distribution channels, and the beef was also unbelievably tough. I didn't get the tenderloin there, but for example got meat from entrecôte (rib-eye), and also the only thing that could be done with it was to grind it, trying to fry it ended up inedible.

I don't think its because of being 100% grass-fed, as I bought some 100% beef from a bit larger, medium-scale farmer in western Europe, who has maybe 50 cows and hangs them after butchering and the meat was as tender as most beef. I know grass-fed beef doesn't have much marbling, so some cuts won't give as good steaks because of lack of fat, but for the tenderloin there should be no difference as there isn't any marbling anyway.

Also I don't think its because of the breed, as the super-tough beef from small-scale farmer in Eastern Europe was Salers which is a well known quality cattle breed, and the farmer was even certified organic.

In both the Asian and Eastern European country, any beef from a supermarket is reasonably tender, only when I buy beef from very small scale operations, its so tough. Does non-professional butchering, not in a abattoir, without hanging the carcass to age a little, is the reason the meat ends up so tough that even the tenderloin is only good to mince for ground beef, and you can't make an edible steak out of anything from the cow? Or is there another major reason for the toughness? I know many factors have some impact on tenderness, like the cow's breed, diet, but I I want to what is most likely the major factor in the situation described above, which make the beef tough even if everything else is done right?