السلام عليكم ورحمة الله وبركاته
Polygamy is permitted in our religion, but it’s a good way and is right. The reason being that Muslims men may marry 4 wives is if we compare the women population to the men population, there are millions of more women than men. So who will take care of these women, and this is to avoid prostitution.

In Christianity, man can marry only one woman but he can have numerous lovers as long as he can, as long as he want and hide them from your wife. And he can quickly change lovers and have relation with many women before, during and after marriage. Which the way is right????

The Quran, allowed polygamy, but also restricted it:
"If you fear that you shall not be able to deal justly with the orphans, marry women of your choice, two or three or four; but if you fear that you shall not be able to deal justly with them, then only one" (4:3).
This verse of the Quran was revealed after one of the battles, in which dozens of men were killed leaving behind widows and orphans.
The Quran, limited the maximum number of wives to four under the strict condition of treating the wives equally and justly. In Islam, polygamy is only allowed, and is not the norm. It only provides a moral and practical solution to a situation in which there would be a great number of widows and orphans (like after a war or epidemic for example), who would otherwise be very vulnerable and in need of a stable family atmosphere.