I think you may misunderstood the religious situation in Western Romania.
The main part of the population was Orthodox, not Homean, and that means that Roman elites were generally so as well (giving the role of Bishops and Counts in post-Imperial Romania, it wasn't a detail).
Even the Barbarian elites, that generally were identified by Homean beliefs (except for Anglo-Saxons, Franks or Burgundians for a time) were actually more mixed with an increasing part of Orthodox believers with time (by mixing with Roman elites mostly).
(Granted, you had in a same Barbarian people mix of Pagans, Niceans, Homeans, Jewishs, etc. What determinated the political, and therefore religious, identity of Barbarians tough was the relationship with the king. And these were generally such).
What prevented Homeism to disappear earlier was it was considered as an identitarian feature, dividing Barbarians (that were more and more romanised with time) and Romans. More the population became a mix between Roman and Barbarian features, more it became irrelevant.
It should be noted, furthermore, than using "Arian" for the Homean beliefs is misleading. Homeism was some sort of "soft Arianism", much less antagonizing than the more "hardliner" stance.
Not just a detail, as it's a reason why it was relativly more accepted by populations when you didn't have anti-Nicean reactions (that were usually not religious persecutions per se, but rather a tentative to replace the Nicean clergy and its political influence. Generally, it backfired)
Not that having an Homean Christianity eventually dominating is ASB, far from it. But you'd need an earlier PoD where the Roman emperors doesn't favour Nicean clergy and maintain their favours to the Homean beliefs.