Islam didn’t forbid polygamy but it restricted and regulated it. In Islam, it is not compulsory to marry more than one wife but it is permissible for genuine reasons.
A man can marry a second wife if he can demonstrate full respect, justice and impartiality to his wives. Verse, Chapter 4 in the Quran indicates clearly that a man cannot marry more rightly and impartially.
Also, the verse puts a limit of four wives only for unbiased and fair husbands.
Before this revelation, men used to have scores of wives with no limits or conditions.