The answer is simple: because both Trump and the leadership of the Christian right are both morally bankrupt and demagogic. Although he has no real religious beliefs, Trump cow-tows to those l leaders because he wants their political support and the ability of those demagogic religious leaders to persuade (delude) their flocks to act in the political manner which they preach. Those corrupt evangelical leaders overlook Trumps corruption and total lack of morality because they want to use Trump to gain the political power which they can use to enact their religious demagoguery into law and use it to control people.