It seemed like that was popular with some working class blacks as well.
That policy was generally NOT popular among non-whites. It WAS popular among most whites. Law-revering people of all colors can still not like the strident "Build That Wall" rhetoric. But, it did resonate with one demographic more than others. Not to the exclusion of others, just more with one group than others.And how does that policy resonate more with white voters than with non-white? The only people opposed to border security are illegal aliens and the progressives who support them to promote intentional subversion of the rule of law. Generally speaking, legal immigrants (even the "non-white" ones) support enforcement of immigration law.
The Venn diagram does have some non-whites supporting it, and some whites not supporting it.
But, for EC math purposes, those cancel out. He needed a majority of the 40% of that demographic to vote for him. It appears that worked.
Another policy/strategy was to not denounce the white supremecist faction. White people who are not racist don't really care about that.