No, horses could not have banded together and fought back. Humans have almost never accepted a backslide in quality of living. All the examples I can think of are because of short lived war time austerity.
Britain experienced an economic collapse in the early 5th century AD after the Roman Empire left. Economic activity and urban life decided, and buildings were abandoned. Their supply chain was suddenly much more limited, and localized to specific areas, whereas before, the Roman Empire had allowed them to trade with other countries more. Their standard of living didn't really change for the next few centuries. I won't compare beyond that.
For example, in Korea during the Joseon/Chosŏn period, the status of women gradually declined due to Neo-Confucianist ideology. Women stopped inheriting property in the seventeenth century. They lost the right to intiate divorce, while men could still intiate divorce under seven grounds (disobedience to parents-in-law, failure to bear a son, adultery, jealousy, hereditary disease, larceny, and talkativeness). Widows lost the right to remarry, and were seen as inconvenient for the family. Women were forbidden from playing games, partying outdoors, and riding horses.
The decline of women's rights happened in other societies, too; I just happened to have a book about Korean history on my desk.
North Korea, after the Korean war, their living conditions got way way worse than when under Japanese occupation, even though their military has improved.
Afghanistan, since it's been overtaken by the Taliban, even though they are mightier from a military standpoint, the living conditions have become worst.
The Soviet Union post WWII, they came out of it as a military superpower, but the damages from the war meant their living conditions were way worse.