What are the reasons behind Samudragupta's campaign?

Samudraguptas dakshinapatha campaign...

What is the real reason behind the campaign?? Is it plunder of wealth for one time? Because he couldn't continue to collect wealth as approval of suzerainty for long... He didn't even annex.

Few sources say it is to promote vaishnavism to the south can be seen as foundations for Hinduism in south??... I could see this answer from few sources but couldn't substantiate much.

The main source throwing light on the military exploits of Samudragupta is the Allahabad pillar inscription which was composed by his court poet Harisena. The long Inscription enumerates the people and countries conquered by Samudragupta.

The places and the countries conquered by Samudragupta can be divided into five groups.

Group one includes the princes of the Ganga-Yamuna doab who were defeated and whose kingdoms were incorporated into the Gupta Empire. Here the Achutas, Nagasena and Kotas. In all nine kings of Aryavrata including Rudradeva, Mattila were defeated.

Group two includes the rulers of the eastern Himalayan states and some frontier states such as Samatata, Davaka, Kamarupa, Nepala, Kartipura. It also covers some of the republics of Punjab like Malavas, Arjunayas, Yaudheyas, Madrakas, Abhiras, etc. The republics which flickered on the ruins of the Mauryan Empire were finally destroyed by Samudragupta.

Group three includes the forest kingdoms situated in the Vindhyan region and known as Atavika rajyas, they were brought under the control of Samudragupta.

Group four includes the twelve states of the eastern Deccan and south India. This campaign is known as the Dakshinapatha campaign. The rulers here were conquered and liberated.

Group five includes the names of Shakas and the Kushanas, some of them ruling in Afghanistan. It is said that Samudragupta swept them out of power and received the submission of rulers of distant lands.

The main factor that guided Samudragupta in his campaign was

1) His imperial ambition to extend the influence of Gupta dynasty to as far area as possible.

2) Geo political factor. The Nagas were important power in Aryavrata region. So, in any scheme of expansion of Gupta Empire, it was but natural that the Nagas would have to be subjugated first.

3) Economic factors were also paramount, as this was especially true of the Dakshinapath campaign, Samudragupta was lured by the rich wealth he could acquire as presents and tributes from the southern states.

Conclusion: The policies adopted in terms of conquests by Samudragupta varied. While for the states of Aryavrata, he adopted the policy of complete subjugation and annexation of their territories, in case of south India, he was content at establishing his suzerainty and extracting tribute from them. Towards tribal and frontier states, the policy was no more than extending some sort of general control.