Since it seems like you're genuinely curious, I'll offer what insight I have (which isn't much). I'm not a farmer but I've lived around farmers and get my food from community-supported agriculture (CSAs) wherever possible, which puts me in direct contact with farmers a lot, and we talk.
In a lot of areas, John Deere is the only company with local distribution, meaning that if you want to buy a new tractor, you have to either buy John Deere or pay for delivery. The new alternatives are not particularly good, either, since economies of scale force them to either charge more, or cut quality to cut cost. Kubota, for example, is one of the few alternatives with wide distribution, but are known for quality issues.
The alternative which most smaller-scale farmers seem to prefer is actually buying used, but that preference is reflected in the price: good-condition used tractors from the 80s or earlier run for about 3x the price of equivalent new tractors. Most of these old machines were overbuilt and therefore don't break down often if maintained well, but when they do break down, parts aren't available and mechanics don't know how to work on them. The CSA I went to in upstate NY had a farmer on staff who knew how to work on their two tractors--and pretty much only those two. And building a patchwork tractor fleet out of various different used tractors obviously scales poorly.
Tractors are possibly the least complicated machines John Deere sells, and for many of the products they sell, such as tillers, planters, etc., they have no large-scale competition, and some of these machines didn't exist 40 years ago, at least not in their modern forms. With the exception of a pull-behind tiller, the CSAs I've been to don't have this equipment, instead doing this labor by hand. Part of the reasoning behind this is that it's more sustainable, but I suspect that's at least partly putting a positive spin on being priced out. Modern versions of these complicated machines are more reliable than older versions because they coordinate the complicated interactions digitally (no moving parts involved in coordination) rather than mechanically. This digital control is precisely where John Deere is violating the GPL and people's right to repair.
Finally, some farmers are locked in by inertia: they bought and trusted John Deere for generations before John Deere started using software monopolistically, and didn't experience any of the problems until their newest equipment started breaking down, which might have only happened recently.
In general, part of the fallacy of anarcho-capitalism is that unregulated competition is stable: eventually one competitor becomes dominant and can use that position to no longer have to compete on serving the customer's needs. That's where John Deere is, and they'll continue to behave monopolistically as long as they are allowed to. True capitalism requires a strong central authority to prevent anti-competitive practices through regulation. If anarcho-capitalists really believe that unregulated capitalism results in the best results for consumers, then they should have no problem with regulating in favor of consumers, since it's just making rules that companies have to do what they're going to do anyway.
