The Golden Chain and the Prophetic Hadith

It's an interesting question of that shift from spoken to written, or oral to written. It happened with the pot of an, happened with the crown quite early, and then it also happened with what later becomes the hadith. So why is it, for example, we have Abil Hanifa,. He's the earliest, he's the imam medic, imam shefe, imam habab, didn't happen. Now they're in a line of development, this tradition that we're talking about.