That’s why knights were armored horsemen - heavy lancers.
Foot soldiers wore less armor - helmet, breast and back, and tassets.
True. However, by Agincort the French had a century of experience that heavy cavalry assaults against entrenched bowmen was just a way of dying tired. Turns out horses with arrows in them become a little hard to control.
The English knights had, in these battles, fought on foot.
So the French decided the answer was for them also to fight on foot.
Apparently not realizing that standing and waiting means the English knights will be a little fresher than the Frenchies will after slogging thru a half mile of mud.