Why? Jesus Christ defined marriage as the union between one woman and one man for a lifetime. If you divorce and remarry then you are committing adultery. A union between two people, one or both of whom having been married before and the former spouse is still living, is not marriage as defined in the Bible. Neither is a union between two people of the same sex. Different types of apples, if you want to use the fruit comparison, but apples nevertheless.
If it is not marriage, then what was Moses 2nd union? Was it condemned by God? What did Jesus have to say about being enevenly yoked? There is no contradiction of God’s Word except within our own limited understanding. I try not to be a Pharisee.