Cases of polygamy were not sanctioned by God. They are in the Bible as examples of sinful ways of life; not even Jacob got away with it without being burned. Abraham was monogamous apart from his tryst with Hagar. Isaac was never mentioned as being polygamous either, but monogamous with Rebekah. Esau was a polygamist. David and Solomon were especially plagued because of their polygamy.
The first example of a polygamist in the Bible is the first man to be named Lamech, a sixth-generation descendant of Cain’s line (from Genesis 4), and he is mentioned as being a shameless murderer to boot.
In sharp contrast, sodomy is completely forbidden - in both the OT and the NT, not to mention all of Holy Tradition, the Natural Law, and the teachings of the Church for the last 2,000 years. St. Paul calls it an "abomination." Moses mandated the death penalty in all cases for sodomy (two guys).
Sodomy is a capital felony, polygamy is more like a minor misdemeanor in comparison.