Enchanting Netherite sword in 1.16
The bane of arthropods, smite, and sharpness enchantments are incompatible with each other, meaning you can only have one of them per weapon. You will have to combine your sharpness III book with a different sword or use a grindstone if you want to use it.
As @AwesomeGamer333 wrote, those enchantments are incompatible, as you can see:
I suggest you check this summary of enchantments table, this may help you to plain your future enchantments.