CRP came about because of soil erosion. In the North Central region (IA, IL, IN, MN etc) it was primarily a slope issue. In the Great Plains (OK, KS, NE etc) a wind issue. Soils were categorized based on being highly erodiable due to soil type and slope or wind. This was at a time (like you said 80s ish) when very little adoption of min-till and no-till farming practices. If highly erodiable soils the farmer & landowner had a choice if they wanted to remain eligible for government payment, put it in CRP or change tillage to min/no-till to conserve the soil reduce/eliminate erosion. These were 10 year contracts. Some opted out and continued current practice. Many entered the program because they didn't have the equipment to change and in many areas the agronomy, engineering, economic (compaction, tempt, yield etc) research was not there for these new practices. After the first 10 contracts and the second 10 yr the research and new practices had caught up and more and more land came back out of CRP, more so in NC than prob GP region.
On average farmers own maybe 10% of the land they farm, larger farm operations less than the avg. I know of a 6k+ acre operation where its only 4%. If a farmer had a 10 year cash rent contract (10 would be highly unusual) with the landowner they could put it in CRP and net the difference. But for most why would the landowner let the farmer operator take all the payment if the landowner can take the contract themselves? Most arrangements back then were sharecrop or short 2 or 3 year cash rent contracts.
No farmers didn't throw all there land into CRP because they could make more money than growing crops. It was an environmental issue and also issue for land owners & operators who wanted to remain eligible for other gvt programs. If you want to sign up for the full lecture let me know, there's a lot more to it.
Your welcome. And sorry in advance for spelling grammatical errors, on tablet not gonna proof read and edit.