He's always interesting, IMHO, but he's doing some straw man crap I didn't care for.
Henry V beat the French by maneuver, leading them into a spot with favorable ground for himself, and took the time to set the whole thing up. Also, there was indeed turmoil in the French succession, and the French at Agincourt were arguing about who should lead the battle.
Henry V's victory wasn't unprecedented -- in the prior century, Edward III had similarly used the longbow to defeat the French at Crecy.
the Agincourt keyword, sorted:
The only weapon that was even close to effective was the crossbow, which suffered both from much longer reload time and shorter range.
It was a similar situation to the Kentucky long rifles at the battle of New Orleans where the Brits had an extraordinarily long kill zone to march across before they could even get within range.