elders and deacons are to be examples for the church to follow. that chapter lists many qualities that all followers of Christ are to strive for, including having one wife. these qualities are especially to be exemplified in those who would seek to be leaders of Christ's flock.
seeing as people like david and Solomon who were leaders of israel in the old testament narrative had many wives(which turned out to be a negative for them in that it lead them to idolatry) and God saw fit to see that leaders in the new testament church were to have only one wife, God never approved of polygamy. similar to how he never approved of divorce even though God allowed it because of our sinfulness(matthew 19:7-8, malachi 2:14-16).
couple that with the fact the Jesus only has one wife which is the church as all true followers of Christ are part of the body of Christ(ephesians 5:22-33, 1 Corinthians 12:12-14, revelation 19:7-9).