Ramban famously defines Sefer Shemos as the Book of Exile and Redemption. Ma'amad Har Sinai and the construction of the mishkan are included in the Sefer because
the exile did not end until the day [the people] returned to their place and returned to the stature of their forefathers ... when they arrived at Mount Sinai and built the Tabernacle, and the Holy One, Blessed is He, once again caused His Shechinah to dwell among them at that point they returned to the eminence of their forefathers of whom, "the Counsel of God was over their tents" and, they themselves were the Divine chariot. Then [the people] were considered redeemed. [Introduction to Shemos, Artscroll Translation]
Redemption is a spiritual category; it is measured by connection and spiritual proximity to HKB"H. Thus Bnei Yisroel were first considered redeemed when HKB"H caused His Shechinah to dwell amongst them.
This is clearly Ramban's point. So why does he twice emphasize that redemption entails returning to the stature / eminence of their ancestors?
Ramban is preemptively addressing the following issue. Granted redemption is to be defined spiritually, not politically or geographically. [Political redemption is instrumentally - not ultimately - significant because subjugation interferes with avodas Hashem. (See Berachos 17a; Rambam Hilchos Teshuva 9:2.) Eretz Yisroel is of paramount spiritual significance because it is "the land of Hashem." (See Ramban Vayikra 18:25)] But the definition of hashro'as haShechinah seems unrealistically high. Ramban's response: what was achieved once can be achieved again. Avraham, Yitzchak, and Yaakov were titans whom we revere; but they are also our forefathers. Our genetic material and spiritual capacities derive from them and thus while their example inspires reverence, it also obligates and inspires us. "A person is obligated to say, 'when will my actions match those of my forefathers'" (Tana D'vei Eliyahu.)
A word of reflection and introspection. Spiritual achievement depends on spiritual aspiration. If we shortchange ourselves in our aspirations, willy nilly we will come up short in realizing our potential. The mediocrity of our spiritual aspirations is one of the Achilles' heels of our generation. To transcend the numbing materialism of our times and attain kirvas Elokim we must first aspire to such transcendence. To focus on olam haboh values and eschew olam hazeh values we must first aspire to attaining and maintaining such focus.
Redemption awaits, but inspired aspiration must precede.