Why did Shri Rama take the help of weaker Sugriva but not strong Vali?

 

Shri Rama did not know the existence of Sugriva or Vali or Vanaras in Kishkinda area, while searching for Sita, alongwith Lakshmana.

a) After an encounter with Kabandha, his overlong arms were cut off by Shri Rama and Lakshmana. Kabandha requests Shri Rama to incinerate him, so that he would get his divine form and then would be able to give some clues in regaining Seetha.

After incinerating him, Kabandha assumes his original divine form, and directs Shri Rama to visit Sugriva, who is a righteous person and ill-treated by his brother Vali. He also states that Sugriva is an adherent to TRUTH - सत्य संधो.

श्रूयताम् राम वक्ष्यामि सुग्रीवो नाम वानरः |
भ्रात्रा निरस्तः क्रुद्धेन वालिना शक्र सूनुना || ३-७२-११

"Oh, Rama, listen what I tell... a vanara is there by name Sugreeva, who is vengefully reneged by his brother Vali, the son of Indra.”

वानरेन्द्रो महावीर्यः तेजोवान् अमित प्रभः |
सत्य संधो विनीतः च धृतिमान् मतिमान् महान् || ३-७२-१३

"He that Sugreeva is a masterful one among vanara-s, highly mettlesome, self-resplendent, and illimitable is his self-radiance... and he is also truth-bound and culture-bound... a mastermind, master-hand and a taskmaster.

गच्छ शीघ्रम् इतो वीर सुग्रीवम् तम् महाबलम् |
वयस्यम् तम् कुरु क्षिप्रम् इतो गत्वा अद्य राघव || ३-७२-१७
अद्रोहाय समागम्य दीप्यमाने विभावसौ |

"Oh, bold one, you go straight from here to that great mighty Sugreeva, and oh, Raghava, on going from here now and promptly you fraternise with Sugreeva... and to not to bode any ill of unfriendliness among you two, you make him a friend before blazing Fire, making that Fire as an Attestor of your friendship.”

—-

b) So, Shri Rama learnt about the 2 brothers Vali and Sugriva and about their nature, from Kabandha.

Shri Rama’s siding with Surgreeva is due to the following reasons.

• Kabandha is a 3rd party to Vanaras. He has neither enmity nor friendship with them. So, he must have told the TRUTH. Shri Rama believed his version
• Shri Rama is an adherent to TRUTH and Dharma, and Sugriva, is also adherent to TRUTH. Hence, he naturally got drifted towards Sugriva.
• Kabandha’s version was repeated by Shri Hanuman. Shri Rama keenly observed Shri Hanuman and believed him. So, Shri Rama got the confirmation of the Kabandha’s version of Sugriva.

——

c) When Sugriva challenged Vali for the 2nd time, on the same day, Vali’s wife Tara advices him about the friendship that took place between Shri Rama and Sugriva and advices him to make Sugriva as the Prince regent of Kishkinda kingdom.

However, Vali did not pay heed to her advice.

अयोध्य अधिपतेः पुत्रौ शूरौ समर दुर्जयौ |
इक्ष्वाकूणाम् कुले जातौ प्रथितौ राम लक्ष्मणौ || ४-१५-१७
सुग्रीव प्रिय कामार्थम् प्राप्तौ तत्र दुरासदौ |

"Those that are born in Ikshvaku dynasty, sons of the king of Ayodhya, valiant and unconquerable ones in war, called Rama and Lakshmana are there in this country. These two unassailable ones have chanced there at Sugreeva's place to fulfil the longing desire of Sugreeva.

यौवराज्येन सुग्रीवम् तूर्णम् साधु अभिषेचय || ४-१५-२३
विग्रहम् मा कृथा वीर भ्रात्रा राजन् यवीयसा |

"Oh, king, let Sugreeva be decorously and quickly anointed as prince regent, and oh, resolute one, let there be no hostility to your own younger brother.

—-

d) Coming to issue of as to why Shri Rama did not take the help of Vali, who said at the death bed that he would have brought back Sita, we have to remember that it is an example of hindsight bias.

सुग्रीव प्रिय कामेन यद् अहम् निहतः त्वया |
माम् एव यदि पूर्वम् त्वम् एतद् अर्थम् अचोदयः |
मैथिलिम् अहम् एक आह्ना तव च आनीतवान् भवेः || १-१७-४९
राक्षसम् च दुरात्मानाम् तव भार्य अपहारिणम् |
कण्ठे बद्ध्वा प्रदद्याम् ते अनिहतम् रावणम् रणे || ३-१७-५०

"For which purpose I am killed, intending to do good to Sugreeva is incidental to it, you should have assigned me for that purpose in the first instance itself, and I would have brought that evil-minded demon Ravana, the abductor of your wife in one day, that too without killing him in any fight, but by fastening him by neck, and I would have presented Maithili to you. 

——

Had Vali really desired to help Shri Rama, he should have approached him for friendship. However, he disregarded Tara’s advice and went for fight with Sugriva for 2nd time.

Hence, Shri Rama did not do any senseless thing in joining hands with Sugriva.