Answer: They didn’t record the words of the teacher in the past but learned orally, not because it was difficult to record on wooden tablets, for example, but because the students heard and attained the upper world while processing the profundity of the words of the teacher.
Now the situation is different; we hear and record to know mechanically, not through living attainment. When a student follows his teacher like a lower Partzuf following an upper Partzuf through adhesion with it, a living picture of the upper world is revealed to the student. Therefore, the student receives his attainment “mouth to mouth” from the higher level, meaning through sharing a Masach (Screen) with the teacher.
This is called “writing on the tablet of your heart” on the corrected desires. And today people learn dead letters and words because there is no Light in them; there is no characteristic of bestowal, only external knowledge. This is called exile from the upper world.
So, after the fall from the level of spiritual attainment happened two thousand years ago, they began to record the words of the sages of the Torah so that when we would leave the exile in the future, we would ascend to love and bestowal and could revitalize their texts through the upper Light.