Shriya
This has been analyzed, and given the timelines, the 2 Nahushas have gotta be different. The Nahusha who was the father of Yayati was different from Mr Ashokasundari
The Chandravansh lineage initially runs like this:
Chandra & Tara => Budh (This is controversial in & of itself, since Tara was Brihaspati's wife 😆)
Budh & Il => Pururavas (This story is narrated by Rama in the Uttarkand of Ramayan)
Pururavas & Urvashi => Ayush (& other sons) (hence Arjun's refusal to marry Urvashi - she was his ancestress)
Ayush & Indumati => Nahusha
Now, Nahusha's son is Yayati, but the wife that he begat him from was not Ashokasundari. She had a different name, and no mention is made of his other wives.
Given that Rama narrated the story of Budh & Il, and given that Bharat's & Shatrughan's descendants were dethroned by the Druhyus, it's more likely than not that Rama's contemporaries would have been no earlier than Pururavas, and not much later than Druhyu. Nahusha would have become devraj after the Indra killing of Vritra, which would have happened in the Satya yuga.
The Ashokasundari stories are pegged around the Treta Yuga, which was when Ganesh came about. Ashokasundari was supposed to have been much older to Nahusha. But if Nahusha existed during the Indra-Vritra era, no way could that have happened.
Given these complications, a clean conclusion is that there were 2 Nahushas - a good Nahusha (in my avi) whose wife was Ashokasundari, and who killed the asura Hunda, and the good-turned-bad Nahusha, who went after Sachi, became a snake for 2 yugas, captured Bhima and only let him go after Yudisthir agreed to a bhashan exchange on caste.
That's the other thing not believable: why would Mahadev/Parvati encourage the marriage of their daughter w/ someone who'd display lecherous behavior towards the queen of the devas? Or allow her to live unprotected for 2 whole yugas?