I think it's partially because of the negotiations with the Tolkein estate that the movies turned out as great as they were.

If no negotiations were needed, then anyone could have picked up and done a low-budget adaptation and called it a day.

But, because there were some rather expensive and difficult negotiations to settle, the amount of people able to do the movies was limited to those who would be able to spend the money to get the rights. And with that sort of investment, there's a big incentive to also invest heavily in the quality of the production to ensure a good return.