If the exile meant nothing more than atonement for sins, it should have become progressively less severe, as each successive period brought partial atonement. In fact, however, we observe that the exile is becoming ever more intense, while G-d's presence is becoming less and less manifest. The earliest days of the exile were illuminated by giants of the spirit, the tannaim; they were succeeded by the amoraim; and in the generations since that time the divine light has become more and more heavily veiled.
It is therefore obvious that the exile has an additional, inward content.
The innermost function of the exile is the ultimate revelation of a new light. The greater the divine focus on this new revelation, the more the [present] flow of divine light is deferred. (This concept is explained in the next section). Hence, the greater the divine focus on the future Redemption, as we draw closer to the coming of the Moshiach, the denser does the exile become.
Likeuti Sichos, Vol II, p. 361
From: MiGolah LiGeulah - From Exile to Redemption