D&C 58

From an eternal perspective, as the Prophet Joseph Smith was experiencing great tribulation in the Liberty Jail, the Savior said -

"My son, peace be unto thy soul; thine adversity and thine afflictions shall be but a small moment;
8 And then, if thou endure it well, God shall exalt thee on high..."  (Doctrine and Covenants | Section 121:7 - 8)

Almost, as if to suggest that which was yet to come as the saints established the center of Zion, the Lord taught much the same as He did to the Prophet-

"...blessed is he that keepeth my commandments, whether in life or in death; and he that is faithful in tribulation, the reward of the same is greater in the kingdom of heaven.
3 Ye cannot behold with your natural eyes, for the present time, the design of your God concerning those things which shall come hereafter, and the glory which shall follow after much tribulation.
4 For after much tribulation come the blessings. Wherefore the day cometh that ye shall be crowned with much glory; the hour is not yet, but is nigh at hand."  (Doctrine and Covenants | Section 58:2 - 4)

I sense that the Lord  was teaching why they were there at this point knowing the events that would yet follow -

"Remember this, which I tell you before, that you may lay it to heart, and receive that which is to follow.
6 Behold, verily I say unto you, for this cause I have sent you—that you might be obedient, and that your hearts might be prepared to bear testimony of the things which are to come;
7 And also that you might be honored in laying the foundation, and in bearing record of the land upon which the Zion of God shall stand..."  (Doctrine and Covenants | Section 58:5 - 7)

"...that the testimony might go forth from Zion, yea, from the mouth of the city of the heritage of God—
14 Yea, for this cause I have sent you hither..."  (Doctrine and Covenants | Section 58:13 - 14)

Even though this was the center point of Zion, which place they would be forced to leave, it was essential to establish the foundation of Zion, and to willingly bear record and testimony that the center place of Zion was established.  And from there, Zion or its stakes of Zion would grow throughout the world.

I also sense that the Lord was also suggesting though this land would be the center point of Zion and where the gospel would go forth to all nations, I also believe that the Lord was also suggesting that He knew the saints would be forced to leave and that the complete development of the center of Zion was to be fully developed at a later date saying -

"And now, verily, I say concerning the residue of the elders of my church, the time has not yet come, for many years, for them to receive their inheritance in this land, except they desire it through the prayer of faith, only as it shall be appointed unto them of the Lord."  (Doctrine and Covenants | Section 58:44)