Reagan's Fed chairman, Paul Volcker, put the breaks on the expansion of the money supply in 1982.
I imagine the bankers who urged the loans knew that would happen sooner or later. (Not everyone went for it, and the careful were generally rewarded by keeping their farms).
By '86, not only were ag prices in the toilet, but the oil patch (where many farmers went to work to make extra money) was dead--as in 2 rigs drilling in an area that now has nearly 200.
Many lost everything, auctioned off at fire-sale prices.