From my reading of Mahabharata Yadavas do not appear to be a strong or prominent clan in India prior to the rise of Shri Krishna.
Rather most other high houses of bharata seems to look at Yadavas with a bit of disdain. Is it true? Does anyone know why ?
What is the historical origin of Yadavas?
Lord Brahma had a son named Atri and Atri had a son named Soma or Chandra (the Moon god). Budha was son of Soma.
Lord Brahmā had another son named Marīci and Marīci had son named Kaśyapa. Vivasvān (the Sun god) was son of Kaśyapa. From Vivasvān was born Vaivasvata Manu. Vaivasvata Manu got a daughter named Ilā.
Thus Budha begot in her (Ilā) womb a son named Purūravā.
In Purūravā's lineage then born kings like Nahusha and Yayati. Yayati's eldest son was Yadu.
Yadu's descendants came to be known as the Yadavas.
This lineage was also known as Mādhava and Vṛṣṇi after kings Madhu and Vṛṣṇi.
(Sources: SB 9.1, SB 9.17, SB 9.18, SB 9.23)
Yayati's youngest son was Puru. Puru's descendants came to be known as the Pauravas, the same lineage came to be known as Bharat Vanshi (after king Bharat), Kaurvas (after king Kuru), Pandavas (after king Pandu) etc.
From my reading of Mahabharata Yadavas do not appear to be a strong or prominent clan in India prior to the rise of Shri Krishna.
Yayati requested the eldest son, Yadu, to take his old age and transfer the youth of Yadu to him. Yadu declined his father's request. Yayati then cursed Yadu. Later on the curse was removed by Indra as mentioned in RV 4.30.17 which is explained in this answer. Yayati din't appoint Yadu as the chief king and gave few territories from South (druhyuṁ dakṣiṇato yadum ~ SB 9.19.22). This is same as how Yudhistra was sidelined earlier, he was not appointed as the king of Hastinapura but Indraprastha.
But Yadu gained popularity, fame by his own virtues deeds.
SB 9.23 mentions many famous Chakravarati kings in Yadavas prior to the rise of Lord Shri Krishna :
Kartavirya Arjuna (He [Kārtavīryārjuna also known as ShashtrAjuna] became the emperor of the entire world, consisting of seven islands ~SB 9.23.24. No other king in this world could equal Kārtavīryārjuna in sacrifices, charity, austerity, mystic power, education, strength or mercy ~SB 9.23.25. He defeated and put Ravana in Jail. He eventually met his death at the hands of Lord Parashurama.)
Madhu (After him, his lineage is called as Madhavas ~ SB 9.23.29. Hence, Lord Krishna is called as Madhav.)
Vrishni (After him, his lineage is called as Vrishneyas ~SB 9.23.29. Hence, Lord Krishna is called as Vrisney. His name is mentioned in Bhagavad Gita 10.37.)
Śaśabindu (possessed fourteen opulences and was the owner of fourteen great jewels. Thus he became the emperor of the world.~SB 9.23.30-31)
So your understanding seems to be wrong, Yadavas were one of the most strongest and prominent clans.
Rather most other high houses of bharata seems to look at Yadavas with a bit of disdain. Is it true?
No. Who are high houses? Yadavas were also from Chndra Vanshi Kshatriyas and Yadu was elder brother of Puru (whose descendants were Kaurvas/Pandavas). So neither by birth nor by power (as described in the above section) Yadavas were inferior.
The answer is provided in Vishnu purana, book 4, Chapter 10 onwards (may be also in other puranas)
King Nahusha had six valiant sons: Yati, Yayati, Sanyati, Ayati, Viyati and Kriti. Yati the first born declined the sovereignity. Yayati became the king.
Yayati had two sons, Yadu and Turvasu through his wife Devayani. He had three more sons, Druhyu, Anu and Puru, through his another wife Sarmista.
Due to curse of Usanas, Yayati became old and infirm before time. Having appeased his father in law, Yayati obtained permission to transfer his old age to anyone who consent to take it.
Yayati requested the eldest son, Yadu, to take his old age for 1000 yrs and transfer the youth of Yadu to him. Yadu declined his father's request. Yayati cursed Yadu that he and his descendants will not posses dominion.
Similarly, when Yayati's request was declined by his other sons Druhyu, Turvasu and Anu, they were also cursed. The youngest son, Puru accepted his father, Yayati's request and transferred his youth to Yayati and in turn took over the old age of Yayati.
After 1000 yrs of enjoyment of loaned youth from Puru, Yayati realised futility of all the material pleasures and restored the youth of his youngest son,Puru and installed him as the supreme monarch of the kingdom. To Turvasu, Yayati consigned the south west provinces; the west to Druhyu; South to Yadu and North to Anu. All the brothers Yadu, Druhyu, Turvasu and Anu were to govern only as viceroys under Puru, who was appointed the monarch.
Due to tbe curse of Yayati, the descendents of Yadu were denied the rights of being full fledged kings. The descendents of Yadu are called Yadavas. In this lineage of Yadu was born Supreme Lord Vishnu as Lord Krishna and Lord Balaraama.
https://www.sacred-texts.com/hin/m01/m01069.htm
Here occurs a sloka regarding (Yayati's) descendants, 'Devayani gave birth to Yadu and Turvasu; and Vrishaparvan's daughter, Sarmishtha gave birth to Druhyu, Anu, and Puru., And the descendants of Yadu are the Yadavas and of Puru are the Pauravas.
https://www.sacred-texts.com/hin/m01/m01096.htm
Yayati was cursed by Rishi Kavya or Usanas of wrinkles and white hair so he requested his son Yadu to give him his youth.
"Vaisampayana said, 'Yayati, then, overcome with decrepitude, returned to his capital and summoning his eldest son Yadu who was also the most accomplished, addressed him thus, 'Dear child, from the curse of Kavya called also Usanas, decrepitude and wrinkles and whiteness of hair have come over me. But I have not been gratified yet with the enjoyment of youth. Do thou, O Yadu, take this my weakness along with my decrepitude. I shall enjoy with thy youth. And when a full thousand years will have elapsed, returning to thee thy youth, I shall take back my weakness with this decrepitude!'
Yadu refused.
"Yadu replied, 'There are innumerable inconveniences in decrepitude, in respect of drinking and eating. Therefore, O king, I shall not take thy decrepitude. This is, indeed, my determination. White hair on the head, cheerlessness and relaxation of the nerves, wrinkles all over the body, deformities, weakness of the limbs, emaciation, incapacity to work, defeat at the hands of friends and companions--these are the consequences of decrepitude. Therefore, O king, I desire not to take it.
Yayati cursed him saying that his sons will never be kings.
"Yayati replied, 'Thou art sprung from my heart, O son, but thou givest me not thy youth. Therefore, thy children shall never be kings.'
