Manufacturing at scale is hard and expensive. John Deere has been doing it for years, creating the most reliable tractors in the world for decades and has only recently decided to bend customers over to give them the ol' in-out-in-out.
A new brand would need to start from almost smaller than scratch, and have tens of million dollars of investment to even get started producing their own tractors. Then they'd have the uphill battle of a set of people who are extremely reliant on these machines to trust a new company with no track record with highly mission-critical equipment.
It would be an incredibly high-risk investment, with little to no guarantee of success.
Instead, as the article says - these farmers are not buying new tractors from anyone at the moment.