What are the major views on Adam's motivation to sin given that he was not deceived?

I cannot see how this question can ever be answered according to any Scripture I know. The only inference I can draw to a possible answer is that without knowing good from evil, unless Adam were with Eve when the Serpent deceived her; he might not know that that fruit his wife gave him was the forbidden fruit. otherwise like all men we know to just eat what our wives prepare for us and keep our mouths shut. one other remote answer would be that he didn't want woman to be smarter than man, at which he may not have succeeded anyway.

What are the major views on Adam's motivation to sin given that he was not deceived?

According to Genesis 3:6, after the woman had eaten, she offered the fruit to her husband who was with her. I see here only a change in panorama, not a change in chronology. Adam had been standing there the entire time. He heard it all, he saw it all. If we look at the first part of verse 6, a possible answer reveals itself.

And when the woman saw that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat... (AV)

We are told that the woman "saw" three things concerning the tree:

1. It was good for food;
2. It was pleasant to the eyes;
3. It was a tree to be desired to make one wise.

To begin with, the woman was motivated by what she now "saw," not by what God had previously declared. And what she saw appealed to the bodily senses and carnal desires. It is no coincidence that a serpent is seen beguiling the woman. That the serpent ("the poisoner") was the mouthpiece of Satan is commonly understood. And in a very real way, here the serpent "poisoned" the thinking of the woman and her husband, "who was with her."

Though no reference is made to what Adam "saw" in the tree, we do have one clear fact revealed to us in Scripture—

...and he did eat.

Irrespective of what Adam did or did not see with regard to the tree, what he DID see was that the woman had eaten of the forbidden fruit and "was not dead." Regardless of Adam's position with regard to the tree, he was still motivated by what he "saw" in stark contrast to what God had declared and commanded. Thus, Adam's motivation to sin was the fact that he did not see the woman fall down dead. Which brings up an interesting point.

Numbers chapter 30 deals in part with the making of vows and swearing of oaths which bind a man or woman. Beginning with verse 6 we read—

And if she had at all an husband, when she vowed, or uttered ought out of her lips, wherewith she bound her soul; 7 And her husband heard it, and held his peace at her in the day that he heard it: then her vows shall stand, and her bonds wherewith she bound her soul shall stand. 8 But if her husband disallowed her on the day that he heard it; then he shall make her vow which she vowed, and that which she uttered with her lips, wherewith she bound her soul, of none effect: and the LORD shall forgive her. (AV)

These are the words of the LORD which Moses, in turn, conveyed to Israel. I submit that there is little difference, if indeed there is any at all, between an oath that binds one's soul and a deed which does so.

Here we have God's own declaration that if the husband hears (or hears and sees) what his wife does which is contrary to God's declaration, command, statute, edict, law, precept, etc., then the man has full authority to disallow what was said or done by the woman (wife) and, "...the LORD shall forgive her."

I see no reason to strip Adam of this caliber of authority. He would have been well within his sphere of authority and dominion over the serpent in disallowing the "act" of the woman, and to give the serpent the "left foot of fellowship" from the garden. In so doing he would have upheld the command of God both in regard to the "fruit" and in regard to "having dominion."