The French mounted knight charged trough a plowed and muddy field, turned into a complete mess by the rain, right into the English arrowrains, wich panicked their horses, their horses ran away, fell, ran onto the sharpened trees infront of the archers, in other words, one big chaos of falling horses. Then, their infantry charged and did the same (mostly dismounted knights) Their progress was slower, since they weren't mounted, and they got even more arrows on them. The French cavalry tried flanking the English positions but they got repelled.
Imagine running trough knee-deep mud, with a full suit of armour, and weapons. Not that easy. Add arrow rain of longbows: chaos.
After the French leaders were killed, the French started to rout.
Is this a good theory?