It's all for his idiot base. Every damn bit of it.

His base will believe that everything he does is the best thing anyone could have done, because they’re brainwashed. As Trump himself said, he could shoot someone on Fifth Avenue and they wouldn’t care. Actually, he could say he already built the wall and they would just take his word for it.

He was ready to cave on the wall until right-wing hate radio criticized him for it. He can’t deal with the notion that Rush doesn’t like him. And that’s the issue.

He knows he has to please his base but...
Ego point 1: He doesn't like being told no, especially by a woman, so he'll fight for anything that he can spin into a victory even if Pelosi gives him a baby gate to put at the border.
Ego point 2: Trump doesn't see legacies as something that should be nebulous like improving healthcare for all people, etc. Legacies are physical objects, preferably with your name on them. Fewer and fewer of those exist for him, but if he can build a wall, it will be, "The Trump Wall," even if he can't put his name in neon letters on it and will last longer than anything else that once bore his name.

TlalocW

Using disinformation, and propaganda to control the news with away from the russia and putin issues.