The myth that the bow, and by extension the longbow, were the atomic bombs of medieval warfare is slowly being quelled. There have been tests shown that the strongest of bows could not even cause injury to mere mail were it supported by a gambeson. But I came across this quote regarding the Third Crusade, where English knights were harassed by Ayyubid bowmen:
"Baha al-Din also described the difference in power between the Crusader crossbow and the bows of his own army. He saw Frankish infantrymen with from one to ten arrows sticking from their armoured backs marching along with no apparent hurt, whilst the crossbows struck down both horse and man amongst the Muslims.[10]
Armor, and definitely mail, are extremely underrated. A properly equipped knight had was usually killed by specialized weapons, or surrounded, mobbed, dragged to the earth and slaughtered. There's a reason they dominated the battlefield during the medieval period. The sooner this, "the longbow" destroyed everything because of Crecy & Agincourt myth is dissipated the sooner we can actually learn the truth about medieval warfare. Armor was worn for a reason and it wasn't because it "looked good".
Mike Loades has a great theory as to why the longbow truly won Crecy. The Knights, trudging through mud, fatigued were being dismounted by the arrows and also taking the impacts. While the arrows were not lethal, being hit by a projectile with a certain amount of mass is greatly taxing. He argues that bowmen actually fatigued the knights to the point that when battle was joined, the longbowmen, in lighter armor, rested, and in great defensive positions, were able to mob up and mob up on the charging knights who by that time probably were completely exhausted.