Every citizen, including Christians, have a right to choose who they want to serve as President. Many Christians voted for Nixon. A lot voted for JFK. Many also voted for Trump. They were not choosing him as Lord, but they hungered for someone who would work to protect religious liberties and strengthen the economy.
Was he the poster boy for morality? Actually, none of us are. According to Scripture, there is only one who is good and that is God. It seems that the other choices for President, Dems and Repubs, were not angels either.
Being a Christian does not necessarily mean one chooses wisely. If I remember correctly, King James of England who commissioned the interpreting of the Bible officially into English, was no saint either. Just sayin.