The thing is, at first they didn't bother trying not to kill each other. The earliest tournies were just a bunch of bored knights gathering on either side of a field and then going at it. Blunted swords were an innovation! In a weird way it was like auto racing. At first nobody gave a sh- about safety. Then people realized it was a way to make money, and they started making it safer. And each step was a real innovation. They had to think up blunting lances, making them frangible, if you're never getting off the horse make that armor as thick as you can, and so on.