One thing I think people miss about Trump's rhetoric is that when he toys with an idea, it's sometimes about feeling out the response. It doesn't have to be limited to seriously floating a plan or just trying to rile up his opponents, it can also be like a person trying on a piece of clothing. You try it on, walk out of the dressing room and guage reactions.
He's not so calculating that he has any sort of singular goal when he acts. He's just throwing things at the wall and seeing what happens, and going from there. He's ultimately, extremely flexible.