This will sound weird, but a lot of Trumpers don’t actually care about the wall, per se.

The Trump administration is looking to reduce and change legal immigration, in some ways making it more like it has been previously or like other countries.  (Immigration levels have not always been this high in America.)  

This makes a lot of sense from a “keep Republicans able to get elected over the next five decades” perspective, as, as we all know, Republican outreach to other minority races has mostly flopped.  Also, views change the more generations that immigrants are in the country.  (I talk about them flipping the Asians, but it’s a bit harder than flipping the Irish since there is a greater visual difference with whites, and so there are limits to how far racism will dissolve.)

The Democrats were celebrating an inevitable demographic tide that would deliver them permanent electoral majority.  However, that tide is not actually inevitable.  On some level, Trumpers can probably sense that the plan is to replace or outnumber them, but America does have immigration as part of its national mythos so this is not as well-supported.

The Wall is, to a degree, just a hammy metaphor for actually enforcing immigration law, and to a lesser degree, changing immigration rules.  If he changes immigration / enforces immigration law in other ways, his voters will be satisfied even without him actually building it.