Know that JD found a way to make that work like this you have to give them props for being bigger a****oles than Cummins.
John Deere manufacturers everything themselves which includes engines and transmissions. There's no one in their supply chain that really has the position to buck them other than the customers themselves and, let's be honest, most won't.
The way I look at it is that most hardware on farm equipment that breaks and is field serviceable like teeth, stalk stompers, and snouts aren't going to have ECUs, and therefore, are still field serviceable. The moment John Deere starts requiring service people to change those parts, the farmers (John Deere is literally costing them money) and service people (why am I wasting time doing something the farmer could do) will revolt.
Farmers don't have the time nor equipment to do a transmission swap where the ECU is used so this doesn't hurt farmers as much as it hurts independent equipment service people which, let's be honest, don't really exist already.
Edit: Let me be very clear: old farm equipment is pretty rare to see. Farming in the USA is all about the economics of scale. Scale means bigger equipment. Bigger equipment means new equipment. I think a lot of US farm equipment gets sold to other countries where there is demand for big machinery but not enough funds to buy new. If memory serves, there is actually companies in the USA that exist for the express purpose of buying used equipment in the USA and selling it abroad.
If I had to guess, Ukraine probably ended up with some of this older equipment that is functionally obsolete in the USA. They likely salvaged the part from a different machine and installed it on a mostly working machine to make it operational again discovering the ECU locks. That's likely when they set off to jailbreak it because the manual labor was already done.