Which is EXACTLY what trump realized about his base in the campaign. He knew they would completely forget about his promises, disregard his dishonesty, make excuses for his past behavior, and generally engage in short-attention-span politics.
And yes, trump’s claim about Mexico paying for the wall was bogus. He knew it then, he knows it now. That said, once trump got a bunch of fanatics to chant with him about it, there ain’t no goin back.