Donald Trump's policies on, well, anything, are fluid. He can switch sides in a matter of seconds, with no regard for how insane and unhinged he comes across. His immigration policies, aka "build a wall", are largely what drew his base of white nationalists, racists and run of the mill bigots to vote for him.
So his both softening and hardening of his immigration policies has perplexed many. In this WERD clip, Stephen Colbert dissects it.