[Numenorean]

Kuru: "Arvedui never struck me as being a particularly strong character. The impression that I have of him is that he was rather weak."

So many people assume that Arvedui was too weak to become High King of the United kingdom, but that may not be the case. Most of his life was an ongoing war with the Witch King, a state of affairs that would surely harden the disposition of any who lived through such times. He clearly did not have the military/economic/seafaring might of Gondor at his disposal and coupled with a fundamental lack of manpower its a wonder that his line survived at all - but survive it most certainly did, with vast implications for the Race of Man.
Arvedui wisely bid his sons take refuge with Cirdan in Lindon, whilst he covered their flight and held out until the very last upon the North Downs. Only then did he flee North with the Ring of Barahir and the Palantiri of Amun-Sul and Annùminas. Is this weak?
I 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. But I am open to other interpretations of course...