Trump was repeatedly given the opportunity to mention something other than 'lines around the states'. Yet he was adamant about that being all of it.
The one thing I know about Trump is that he knows that the human mind only remembers short phrases and you can only keep an audience’s attention 20 minutes max (ask any preacher). He knows that his followers remember every one of his talking points by heart. What benefit would he gain by explaining in minute detail and muddying the issues. Rubio does a great job of that. Who remembers a word he says?