In olden days, kings used to have more than 1 wife and it was quite common. Even the able king Dasharatha had 3 wives. Today, when we think of polygamy, we can only think that it is for self pleasure. If that was the case then why would such an able king like Dasharatha indulge in pleasure and would feel the need to marry 3 women?
In the past, kings used to marry the daughter of the neighbouring kingdoms so that they build allies with those kingdoms. It was a strategy of the ruler. But Sri Ramchandraji showed that polygamy was not required to be an able ruler. So, what Dasharatha did, was it right? Was it Dharma?
The answer to this is – Marrying one or many, both are not Dharma. The principle for which it is done is Dharma. If a king had many wives for his own pleasure, then it was not Dharma. But if it was a part of the ruling strategy, then it was Dharma.