On the "literal wall" I'm fairly certain that Trump's enemies took him more literally than his supporters.
Additionally, Trump knows about negotiations. You make a BIG ask and then you accept a "compromise" position that gets you what you want.
The left does this ALL THE TIME, but is so used to Republicans being incompetent, they will be screaming about how it's not actually a "wall" when whatever is finally built (fence, increased patrols/manpower, etc...) thinking that his supporters will be angry that he didn't fulfill his "promise".
From what I've seen of his supporters, they are far more "nuanced" about their expectations than the leftists. (Both what the leftists think OF the Trump supporters and what the leftist are, themselves.)
For example, I see leftists saying things like "TRUMP LIES ALL THE TIME!" and most Trump supporters say, "yeah, just like every other politician." The leftists are all aghast because Trump lies like a salesman, not a politician, but the "unwashed masses" see no difference. Politician liars THINK they are being more subtle, but they aren't, and the people have reacted accordingly.