Trump won by spouting a series of half-truths and outright lies. He convinced a large swath of disenfranchised voters that their struggles and hardships are the result of immigrants, of refugees, and of "the liberal agenda". He promised them change and they bought into the lie. Every day since winning Trump has backed down on his various promises, but those people who voted for him bend themselves backwards to accommodate these backtracks into a narrative that fits their original premise of why they voted for him.
TLDR: Cognitive Dissonance