Silver Arrows were invented in the downfall timeline because they were effectively designed as a last resort (perhaps by the Sages or even Zelda herself after she lost the Triforce of Wisdom) with the help of certain Great Fairies to bring down Ganon after he acquired the full Triforce.Perhaps invented immediately after he was sealed as a back-up plan centuries in the making Some lore autist could probably shoot this down in like 3 minutes
>>720259568>Silver ArrowsIt's really wild to me that the Master Sword never kills, but seals Ganon and the Silver arrows are the only things that do the trick. I like that bit of flavor. It made sense in the first game with the Magical (not Master) sword.I really feel like there are a lot of missed opportunities with Zelda lore/continuity, but oh well.
>>720261945It likely had to do with silver being the thing used in legends to kill monsters, so the devs felt like silver arrows would be a good to go with. And like you said, as far as lore is concerned, there is no Master Sword in the first game, so the silver arrows were the back up.