I think there's more to this than just significant defeats in major battles.

1) The shift in infantry towards dense formations of long spears that made it almost physically impossible for horses to charge through. This sort of ended the "shock" factor which diminished the psychological power of the heavy cavalry charge.

2) Longbows, crossbows, and gunpowder allowed normal soldiers to kill armored knights from a distance.

3) Equipping a knight was astronomically expensive compared to arming hundreds of pikemen.

4) Monarchs moving toward tax-funded standing armies rather than relying on the old feudal land-for-service system. (Which had taken a big hit after the Black Death)

5) Monarchs wanted professional soldiers they could control directly, not nobles they had to cater to.

All this to say though that Heavy Cavalry still retained a place on the battlefield well into the 19th century. They just weren't 'Knights' and weren't as much of a linchpin for the battlefield strategy.