Farmers needed loans to get them between harvests, and those were also quite usurious. The land was in relative abundance (even with the "end of the frontier"),

Farmers needed loans to get them between harvests, and those were also quite usurious. The land was in relative abundance (even with the "end of the frontier"), so it's not like it was the sort of anchoring asset that middle class home-ownership today is crocked up to be. But you are right that poor assets or debts are not enough to explain how interests rates are supposed to help or hurt them. The idea is very roughly that lower interest rates unlock investment which causes them to have jobs. The traditional first approximation is regular people live entirely off income and have no meaningful assets or debts, and rich people don't work and just have assets and debts, live off profits/dividends, or even just loans with their appreciating assets as collateral. It is "class as calculus" as I wrote more about in another comment.