Answer:
Though in old time it was a common practice for kings to leave kingdom to their son in many parts (Many of which are in modern India). But unlike other great kings, Chandragupta Maurya renounce his throne in much younger age.
Chandragupta Maurya studied about different philosophy, religions etc and started following Jainism since his early life. After many fights and fulfilling his dream to unite almost all India (Land that starts from Himalayas in the North to the ocean in the south) he started practicing Jainism more rigorously.
On the night of full moon in the month of Kartik (15 days after Deepawali), he had 16 dreams which implied that practicing dharma and self enlightenment would be harder in coming time. Also there will be twelve year of death and famine. (As explained by his Guru Bhadrabahu) Details of all dreams are:
1. The sun setting (Interpretation: All the knowledge will be darkened)
2. A branch of the divine tree (Kalpavriksha) break off and fall (Interpretation: Decline of Jainism and Chandragupta's successors wont be initiated)
3. A divine car (dev-vimaan) descending in the sky and returning (Interpretation: The heavenly beings will not visit Bharata Kshetra)
4. The disk of the moon sundered (Interpretation: Jainism will be split into two sects)
5. Black elephants fighting (Interpretation: Lesser rains and poorer crops)
6. Fireflies shining in the twilight (Interpretation: True knowledge will be lost, few sparks will glimmer with feeble light)
7. A dried up lake (Interpretation: Aryakhanda will be destitute of Jain doctrines and falsehood increase)
8. Smoke filling all the air (Interpretation: Evil prevail and goodness hidden)
9. A monkey sitting over an elephant (Interpretation: Vile, low-born, wicked will acquire power)
10. A dog eating the pudding (kheer) out of a golden bowl (Interpretation: Kings, not content with a sixth share, will introduce land-rent and oppress their subjects by increasing it)
11. Young bulls working hard (Interpretation: Young will form religious purposes, but forsake them when old)
12. Kshatriya boys riding donkeys (Interpretation: Kings of high descent will associate with the base)
13. Monkeys scaring away swans (Interpretation: The low will torment the noble and try to reduce them to same level)
14. Calves jumping over the sea (Interpretation: King will assist in oppressing the people by levying unlawful taxes)
15. Foxes pursuing old oxen (Interpretation: The low, with hollow compliments, will get rid of the noble, the good and the wise)
16. A twelve-headed serpent (Interpretation: twelve year of death and famine upon this land)
Chandragupta maurya was very desperate to become a monk and he consulted all the policies and left the kingdom in the safe hands of his son Bindusar and became a Jain Monk. Because it would have been not possible for Jain monks to survive the famine in Northern India (In city Ujjaini), they moved to southern India (Near Shravanbelgola).
