Submission lets the material world receive Torah

איתא בגמ' ארץ יראה ושקטה בתחלה יראה ולבסוף שקטה.

It is stated in the Gemara: "The earth feared and was still" (Tehillim 76:9) — at first it feared, and in the end it was still.

The Sefas Emes cites the Gemara's reading of the pasuk: the earth first trembled in fear and only afterward grew calm. He will explain what caused each stage.

פי' העולם כולו קיבל חיות פנימיות בעת קבלת התורה לכן יראה הבריאה איך תקבל קדושה כזו.

The explanation is that the entire world received an inner life-force (chiyus penimiyus) at the time of receiving the Torah; therefore creation feared how it could receive such kedushah.

At Matan Torah the whole world was infused with a new inner life-force. This is why creation first "feared" — the physical world was overwhelmed, unsure how it could possibly contain such immense holiness.

וזה עצמו הי' הסיבה שלבסוף שקטה כי באמת הוא פלא גדול שעולם גשמי וחומרי כזה יוכל להתקרב לקדושת התורה והוא ע"י ההכנעה באמת כנ"ל:

And this very thing was the cause that in the end it was still; for in truth it is a great wonder that such a physical and material world could draw near to the kedushah of the Torah — and this is through genuine submission (hachna'ah), as above.

That same fear was precisely what brought the calm. The world's trembling was an expression of true hachna'ah — humble submission — and it is only through such genuine bittul that a coarse, material world can come close to the holiness of the Torah. Once it submitted, it found its stillness.

Summary: At Matan Torah the entire world received a new inner life-force, and creation first "feared," overwhelmed at how it could hold such kedushah. That very fear was itself genuine hachna'ah — humble submission — and it is precisely through such submission that a coarse, physical world can draw near to the holiness of the Torah, which is why the earth ultimately grew still.