It creates an "us vs. Them" narrative. Like christians and muslims or arians and jews. Oldest trick in the book to get your people to comply with anything.

Heavy ties to the construction industry. Like is anyone really surprised Trump, a guy whose entire career is basically building shit and find ways to hustle money out of suppliers and contractors, wanted to build a fuckoff huge wall? He has friends who will scratch his back if he scratches theirs, and it's easy to think other republicans have doners with similar expectations.

Plus it's an low effort attempt to fix something complex with a highly visible solution. "Look we built a wall!"

Simple, easy dumb way to transfer money from public federal funds to private contractors you are leeching off of.