For it must needs be, that there is an opposition in all things... Wherefore, all things must needs be a compound in one... For there is a God, and he hath created all things... Behold, all things have been done in the wisdom of him who knoweth all things Wherefore, men are free according to the flesh; and all things are given them which are expedient.... (2 Nephi 2:11,14,24,27)
Adam and Eve had been given a few very important commandments in the garden of Eden:
In their non-mortal state, Adam and Eve were unable to keep the first commandment without eventually transgressing the second commandment. Why did God establish commandments that seemed to be in conflict one with another? (2 Nephi 2:11)
Lehi testified that "all things have been done in the wisdom of him who knoweth all things" (2 Nephi 2:24). So, anytime we struggle to understand the scriptures or a gospel principle, we need to remember what the Lord said through the prophet Isaiah: "For my thoughts are not your thoughts, neither are your ways my ways, saith the LORD." (Isaiah 55:8)
I'd like to present a few thoughts that, when considered together, have expanded my own understanding and testimony of the circumstances surrounding "the fall".
When placed in the Garden of Eden, Adam and Eve began their "second estate" (Abraham 3:26). This implies the placement of the veil of forgetfulness over their pre-earth experience. They had no memory of pre-earth life when placed in the garden. They had no recollection of the council in heaven, the plan of redemption, or their place in that plan. They were learning everything 'from scratch.'
The mechanics of their introduction into the second estate differed from ours in that they appeared to skip infancy and childhood, but they still developed from a state of child-like innocence.
In their innocent state of mind they probably had no real awareness of how or when to fulfill the command to have a family, and initially were content to defer it.
There was probably more awareness of the command to avoid the fruit of the tree of knowledge of good and evil. It was in terms they understood because they knew how to eat and probably did so regularly.
In caring for the garden, they would have been regularly reminded of the presence of both the tree of life and the tree of knowledge of good and evil.
The phrase "for in the day that thou eatest thereof thou shalt surely die" (Genesis 2:17) contains a footnote referencing Abraham 5:13, and is more acurately translated "for in the time thou eatest thereof, thou shalt surely die." That phrase expresses the inevitable transition to the condition of mortality, which does indeed precede eventual (not immediate) physical death). It's possible that a misunderstanding of that phrase kept Adam and Eve from partaking until they were sure that it was the only way to gain the kind of knowledge of good and evil that God posseses.
It was altogether fitting that they needed to come to a certain understanding of their situation, the commandments they needed to fulfill, and had control over the timing of their decision to partake of the fruit.
Having both been tempted, they eventually realized their need to partake of the fruit to gain the kind of knowledge of good and evil that God possesses. After partaking of the fruit of the tree of knowledge of good and evil many things happened in quick succession, totally altering the nature of their existence and they were taught/reminded of all the implications of their decision:
They had quickly transitioned from a state of blissful (albeit bland?) innocence to one of daunting (perhaps exhilerating?) challenges. Is it possible that, for at least a moment, they may have believed themselves to be lost, doomed, even cast off to be forgotten because of their transgression?
If so, this state of mind would have been a receptive place in which to have the plan of redemption made known! Any earlier, before partaking of the fruit, and concepts like "sin", "sorrow", "atonement", and "repentance" would have been devoid of any real significance.
24 And we see that death comes upon mankind...; nevertheless there was a space granted unto man in which he might repent; therefore this life became a probationary state; a time to prepare to meet God...after the resurrection of the dead.
... 27 But behold...it was appointed unto men that they must die; and after death, they must come to judgment, even that same judgment of which we have spoken, which is the end.
28 And after God had appointed that these things should come unto man, behold, then he saw that it was expedient that man should know concerning the things whereof he had appointed unto them;
29 Therefore he sent angels to converse with them, who caused men to behold of his glory.
30 And they began from that time forth to call on his name; therefore God conversed with men, and made known unto them the plan of redemption, which had been prepared from the foundation of the world; and this he made known unto them according to their faith and repentance and their holy works.
31 Wherefore, he gave commandments unto men, they having first transgressed the first commandments as to things which were temporal, and becoming as Gods, knowing good from evil, placing themselves in a state to act, or being placed in a state to act according to their wills and pleasures, whether to do evil or to do good--
32 Therefore God gave unto them commandments, after having made known unto them the plan of redemption, that they should not do evil, the penalty thereof being a second death, which was an everlasting death as to things pertaining unto righteousness; for on such the plan of redemption could have no power, for the works of justice could not be destroyed, according to the supreme goodness of God.
33 But God did call on men, in the name of his Son, (this being the plan of redemption which was laid) saying: If ye will repent and harden not your hearts, then will I have mercy upon you, through mine Only Begotten Son;
34 Therefore, whosoever repenteth, and hardeneth not his heart, he shall have claim on mercy through mine Only Begotten Son, unto a remission of his sins; and these shall enter into my rest.