From the Wisdom Surrounding Taking Multiple Wives
So the existence of jealousy in us is only natural, thus it is obligatory that we are patient. Patience is from the fruits of having faith in Qadr (Divine Pre-ordainment) as mentioned by my father and my Shaykh in his book,  and all of the actions of Allaah the Mighty and Majestic are wise. However, this wisdom may or may not become apparent.
From the wisdom surrounding taking multiple wives:
Having more than one wife leads to having more children. Indeed the Prophet (Sallallaahu 'alayhi wa sallam) said, “Marry and procreate for indeed I desire to boast of your numbers before the other nations.” 
The woman may be unable to bear children. Therefore, which situation is better, that the husband divorces her, or that she remains with him while he takes a second wife? Which is better, that the husband does not deserve to have any offspring or that he marries a second wife? The answer is that it is better