Nobody in the Trump camp and hardly anybody in general have noticed the absurdity of the Wall. I lived for the first 4 decades of my life in Arizona, so I have a pretty close view of what is going on. Here it is in outline form.
1. People with money have work that they need doing, but they don't want to pay Americans a living wage or even minimum wage to do it.
2. They let it be known that if people from Mexico can get through, they will provide them with work, no questions asked.
3. A sort of human trafficking infrastructure springs up to get people over and send them along to their jobs.
4. The work is done and everybody is happy, except that now there are too many of these guests, so the rich people sound the alarm - "Look what is going on in our beloved country!"
5. Law enforcement dutifully tries to find the undocumented workers and send them back, but this is hard. It would be fairly easy to find the people causing the problem in the first place - the rich people who hired them and continue to hire them. Follow the money. Law enforcement doesn't want to do that because millionaires don't take too well to being arrested.
6. Candidate for high office calls for a wall, even though most undocumented aliens just fly in these days. Their followers are worked up into a frenzy about this, even though the situation isn't much affecting their lives.
7. And so it goes throughout time - the slaves, the Irish, the Chinese, the Germans all come in, solve our need for cheap labor and then get the unwelcome mat. And so it goes.