First problem: It's big, complicated, specialized equipment. The other manufacturers have been building that for decades. You have been building it for never. It takes a lot of knowledge to build that properly. You will need to design the stuff, get a manufacturing capacity, and then test it a lot. That is not cheap. It's not like the Framework laptop, where they just had to design the enclosure and boards with standard components used by twenty other manufacturers; you're looking at a far more complex business and they can build in bulk and you can't yet. Where do I go to get someone to put up millions for that, especially considering that this was only the first problem.
Second problem: You have to sell and support this everywhere. You may start in one place, but even if you do, you have to be able to sell the equipment to the farmers who want to buy it. That requires people who can demonstrate its benefits, answer questions, and get it out there. When you've done that, you have to support them. You have to have repair parts for sale, repair techs for those who don't want to do it themselves, people to diagnose problems at short notice. It only takes a few failures for farmers to start telling their friends that your company talks about the right to repair because you don't bother having any repair services, and then fewer people will buy.
Third problem: Scaling is hard. If you can build one big farm machine, you still don't have plans for all the other big farm machines that are in demand. I can't tell you which ones you need, but I do know there's more than one of them. Now you have to start doing all the sales and support work you just figured out in lots of places. Keep in mind that even the large, established players don't do that everywhere, and you can see that it's an uphill climb to have a company with the same opportunity to sell as they have.
Fourth problem: They don't want you to win. Up to now, I've only pointed out the problems you have running your company without them even noticing. Let's say you managed that. You can design, manufacture, sell, and support lots of nice equipment. The companies that currently make a lot of profit selling competitive equipment don't want that to keep going. They have more money than you do. They may decide it's time to prevent you from succeeding. They could give your local partners incentives to stop selling and supporting your stuff and switch to theirs. They could cut the prices on theirs, knowing that they can make it back by charging for repairs and you can't (yes, it's worse for the farmers who buy from them in the long run, but not everyone knows that). They can get some of your stuff and research the problems with it, then use that to convince people not to buy. If you're luckier, they come to you and offer just to buy your company. You get money and stop being in their way.
It's not impossible to do, but you need a lot of resources, including time, money, and effort to pull it off. The rich investors don't particularly want to pick a fight with rich companies when they could fund something with fewer enemies. Not many people want to run that company either, knowing that they have to work really hard just to be one of the pack.