The Brit Rishonim that did not include the Land as a party to it, was forged with Moses. Moshe commanded the people to perform the Mount Grizim and Mount Ayval ceremony in order to reintroduce the land as a party to the covenant, to reprise the Brit Avot. The land was indispensable for the same reason that we refer to the Mishkan (Tabernacle) as a Mashkon (collateral). The destruction of the Temples for our sins was a display of the kindness of Hashem in that He allowed His house to revert to simple sticks and stones, to divest itself of the sanctity granted by the Shechina, and to be destroyed. The Temples were the guarantor called upon to pay the debt of the ungrateful and tarnished community that should have paid the ultimate price for its duplicity. In a similar manner, the land had to be brought into the covenant with the people as it too had specific characteristics that had to be acknowledged. As the Torah said, the Land of Israel does not tolerate abhorrent behavior, it is a land that vomits out abominable residents. Like the he-goat and the Temples, it is a guarantor for the Jewish People, to accept punishment on their behalf. It is a land bound by covenant to wait faithfully for her people to return, to remain desolate and unyielding to outsiders attempting to conquer her. This was evident in how the land remained unsettled for nearly 2 millennia after the destruction of the Temple. Many sought to conquer her, yet were repelled by a land that would not open itself up to interlopers. Only over the last century, with the return of the Jewish People, has the Land of Israel started to bloom for her children. All this is part of the Brit Avot that was reasserted by Joshua and the people at Mounts Grizim and Ayval when they entered the land. Tragically, it was the one covenant that Moses was not a party to.
Why did the Torah introduce the prohibition of Bamot, temporary altars, followed by the commandment to seek a permanent place for the Shechina to dwell after the command to conduct the ceremonies at Mounts Grizim and Ayval? Perhaps because of the notion that Mount Grizim, where the blessings were focused, should have been a logical place to build the Temple. In fact, the Samaritans adopted this position, to the consternation of the Jewish People for many years. The Torah tells us that the ceremony at Mount Grizim alone was not sufficient to merit its selection as the ultimate dwelling of the Shechina. After the ceremony it was considered like any other place that held a temporary altar; there was no permanent sanctity ascribed to it. It was like Mount Sinai, Shiloh, Nov, Givon, important places that had temporary sanctity only. There is only one place that will acquire and retain permanent sanctity, and the Torah does not specify it by name. Torah tells us L’shichno Tidrishu, you will have to put forth a great effort to seek and find it. But when you succeed, it will remain sanctified forever. Then as now, the search for Jerusalem and our commitment to hold onto her was a difficult task and mission, but we rely on the promise that it will retain its sanctity forever, and the city and the land will remain faithful to us, just as we remain connected and committed to the Brit Avot and Brit Rishonim that guarantee our connection to the Land of Israel.