There's certainly more to be said, but you might find elements of answer in these posts

Basically, "Arianism" ( a pejorative name for Homoian creed, identifying it with actual Arianism) was a creation of the imperial court adopted by Goths at first to pay-lip service to the emperor (there's no indication Ulfila, their evangelizer, was himself Arian, Homoian or Nicean) and then to maintain a distinct Barbarian "political package" to stress the difference with Romans they were essentially similar to.
Eventually, due to the prestige of Goths after Adrianople and proselytism to other Barbarians (never to Romans, there was actually significant social and legal obstacles to that), this package was adopted by other Barbarians including peoples that had previously adopted a Nicean creed to display good will to the emperor, as Burgundians did.

Liturgical and theological differences between an Homoian and Nicean credo being quite limited, it served to distinguish who was a Barbarian (often a Roman adopting Barbarian social codes) and who was a Roman which was fine with Romans until the former began to rule over them, with the idea Barbarians would eventually "catch-up" especially as the heresies among Romans still existed and possibly "confusing" Barbarians.

The growing and necessary interaction between Barbarians and Roman elites favored a modus vivendi. Mostly, it took the form of Barbarians maintaining privileges and social standing of the Nicean clergy (especially as episcopal career became an important complement or alternative to a changing civil service) the same way the late Empire did.A "Niceanization" looked probable in the early VIth century : Clovis either already converted or was on the verge to, and Alaric II was preparing a "reconciliation" council between Homoians and Niceans, probably leading up to an effective religious switch of western Goths (likely a reason for Clovis to attack when he did, to prevent Alaric's rule in southern Gaul to be thus cemented).

The defeat of Visigoths before Franks (which led to an important political crisis that crippled the stability of Gothic kingship until its end) and the collapse of Vandals and Ostrogoths enshrined both the political triumph of Nicean creed in the west and the disappearance of Homorian creed which relied on a distinct Barbarian elite to exist, at the exception of Gothic Spain. Finally, the "christiaization" of the state (instead of being a "state of Christians" so to say) and the requirement of political and religious unity favored a powerful Nicean clergy, not without internal conflict, especially as the search for a stable Gothic dynasty (which eventually failed) could have found in it a powerful ally.