I hate to say it, but some religious people really are too naive and easily mislead. As long as a candidate says they are against abortion and homosexuality, says that every American has a right to carry a gun, and ALLEGE that they are a born-again Christian, they can get away with a lot, as Trump has proven.
Also, Trump succeeded in badmouthing Hillary. The truth is he is way more crooked than Hillary (Think just Trump university and his disgusting, borderline criminal business practices) but 'Crooked Hillary' is what stuck in peoples' minds. So many impressionable evangelicals believed Hillary is Satan and Trump is the almighty savior sent by God to defeat her, and the rest of those 'evil liberals'.
To summarize, Trump is a great con artist. Many evangelicals will believe to their dying day that Trump is a great Christian man no matter what the evidence against that is. They will only see the kind of man he truly is when God himself gives them a little more wisdom in this matter.