If you read the Bible - especially the Old Testament - you'd see that in a lot of cases, God did not choose saints for leaders. Look at King David and Solomon. I just finished reading about Samson - another judge with a flawed character.
Here is another reason why a lot of evangelical Christians continue to support Trump. He is regarded as the MODERN-DAY CYRUS.
https://www.vox.com/identities/2018/3/5/16796892/trump-cyrus-christian-right-bible-cbn-evangelical-propaganda
Here is the verse about Cyrus:
Isaiah 45
45 “This is what the Lord says to his anointed, to Cyrus, whose right hand I take hold of to subdue nations before him and to strip kings of their armor, to open doors before him so that gates will not be shut: 2 I will go before you and will level the mountains[a]; I will break down gates of bronze and cut through bars of iron. 3 I will give you hidden treasures, riches stored in secret places, so that you may know that I am the Lord, the God of Israel, who summons you by name. 4 For the sake of Jacob my servant, of Israel my chosen, I summon you by name and bestow on you a title of honor, though you do not acknowledge me. 5 I am the Lord, and there is no other; apart from me there is no God. I will strengthen you, though you have not acknowledged me, 6 so that from the rising of the sun to the place of its setting people may know there is none besides me. I am the Lord, and there is no other.
Isaiah 45. Coincidentally, isn't Trump the 45th President?