Two People Learning Together Versus Learning Alone

Avot 3:3

The Mishna says when there are divrei torah between two people the Shechina is among them. Why is the shechina present specifically here?

The difference between two people discussing words of Torah between them versus one person occupying himself with words of Torah.

Delivered at the OU Israel Center, July 9th, 2018 (26 Tammuz 5778)