Arvedui

[Kuruharan]

You're welcome to your opinion, of course.

always deduced that it was a mix of aristocratic provincial pride and shortsighted nepotism that led Gondor to promote a King from within their own ranks (Eänil II)– over the rightful and perhaps wronged Arvedui.

To a degree, you are right, but I think you phrase it badly. I don't think that nepotism is the right word to use in this case. And try to look at it from Gondor's perspective. They were not yet reduced to such straits that they would welcome the rule of a man who amounted to little more than an outlander, who had the appearance of trying to use his claim to the throne of Gondor to save his own skin.

And Arvedui did not behave sensibly when his kingdom fell. He should have gone to Cirdan himself. He also should not have disregarded the advise of the Snowmen when they were informing him of the dangers of their own climate. It is a good idea to listen to the advise of people who know what they are talking about.

Plus, Arvedui was rather high-handed and arrogant in his manner toward the Snowman. Actually he was almost insulting. That alone makes me doubt that he was a particularly good king.

On the other hand, Earnil was victorious in war, and was referred to as being "a wise man and not arrogant."

The Gondorians could only go with the information that they had, like most people. They made what seemed like the better choice (and on the immediate face of things it probably was), who can do more?