Why olden day kings were marrying more than one?

In ancient India, a man could marry with many women. When in current Hindu society, it is not allowed. But it can be read in ancient Hindu scriptures, kings and general peoples were allowed to marry more than one and they were having many children. The question is why such a thing was allowed in ancient time. When the Hinduism is most cultural and civilized religion.
There were many reason to marry with different women. In modern world, it is known as polygamy. First reason is that, in ancient time population of women (female) were more than man (male). Then, it was very difficult to search a capable person for a girl. Girls were on highest peak of sexual desire. Hence, intellectual peoples of that time allowed people of society to follow polygamy to stabilize the social arrangement and want to prevent unsocial activities like rape and malicious relationship.

Second reason for accepting polygamy (Doing marriage more than one) in ancient india was to make a good relationships with enemy and to stabilize the ruling system.
Third reason of polygamy was, by marrying with daughter or Sister of enemy was considered as one of the victory over the enemy by conquering their kingdom. Some time defeated king accept patronage of the victorious king by marrying their daughter or Sister with him to protect his kingdom from destruction.
Fourth biggest reason of ancient king of India were marrying more than one to spread their empire or to full fill the requirement of Army power by the relative king in war. Relative kings were supporting each other in war by supply army and lots of wealth.

Fifth reason is to spread their empire of family, ancient monarchy system was allowing their king or emperor to mary more than one. So the king can provide  more succession to control over the largest empire.

What is Shodoshopchaar and Panchopchar pooja in Hinduism?

In Hindu ritual, some one must have heared about Shodoshopachar puja and Panchopchar pooja. Here, pooja means worship to God. In Hindu, worship rituals Shodoshopchar means worship with 16 offers to God with complete feeling and Panchopchar means only five offering worship. Basically, Shoodoshopchar pooja is specially done on some occasional worship. Panchopchar pooja is done on daily basis. In Panchopchar pooja, 5 things are offered generally, those are Gandh (Fragrance), Dhoop (Fragrance with Smoke or Inccense stick), Deep (Fire lamp with Cow ghee), Pushp (Flower), Naivaidya (Food like fruit or sweets). In Hindu temples, on daily basis God and Godess are being worshiped with panchopchar poojan. But in special occassion or tithis special Shodospchar puja is performed. All these activities are also called as Karmakand. Performing these activities by offering without feelings in mind will not be 100℅ fruitful unless creating feeling in mind.
Also there is a Pooja called Manas Pooja, in which God or Goddesses are not actually offered any physical material but only the worshiper imagine about offering  and create feelings in mind. Such a imagination worship means Manas Pooja   brings 100℅ fruitfulness for devotees.