First, in Genesis, the ideal, created union is given as monogamous. Second, none of the prophets were polygamous. Third, polygamy is usually spoken of disparagingly and as something having disastrous consequences. Fourth, Mosaic law also permitted divorce, but that was a divine dispensation that Jesus lifted and that one existed in the first place because "your hearts were hard". He goes on to say that "it was not this way from the beginning. I tell you that anyone who divorces his wife, unless the marriage is unlawful, and marries another woman commits adultery" (Matt 19:8-9).
Thus, polygamy may have been tolerated for similar reasons, that is, as a concession to the times, as it were. Furthermore, Maimonides argues that while the Torah may permit certain behaviors, a synoptic reading would show that it establishes rules that show these behaviors are wrong.
The biblical great grandfather of the Jews - Abraham - had multiple wives. As did King David who was put forth as a great, but flawed king.
By the time you get to New Testament times, elders in the church could only have one wife, and the admonition of Galatians 3:28 (and others) eventually led to the phase out of these practices - not based on law, but based on love for one another and looking out for one another.
What the Bible shows is God meeting people where they were at and guiding them to a better way over time. These priests should have paid attention to that.