It is certainly important they live in the country and they speak the language very well.
Serbia was very proud that they had their native dynasty and not imported German one, unlike most countries in the Balkan region.
Slovenia, Croatia, Bosnia and Hungary were ruled by the Habsburgs, Romania by Hohenzollerns, Bulgaria by Saxe-Coburgs, Greece by Wittelsbachs and Schleswig-Holsteins, Albania by Wieds etc. It was always pointed out that, unlike these countries Serbia never had foreign sovereign, so Serbian people expect from his "King" to be more Serbian than the others, to be the role model of an leader, soldier so that they could be associated with him, respect him and at the same time fear him.
For Serbian that can't be said for someone who doesn't know the language, has feuds with other members of the family, allows to get booed in public, make really hilarious mistakes while speaking and doesn't live in the country.
It is remarkable how Crown Prince Alexander is respected by foreign royals and people abroad, while in Serbia he just can't find "that" connection with people and they make fun of him and in general do not respect him.
Unlike for example, Prince Tomislav, who wasn't an angel at all. He was a great womanizer, had many mistresses, but never allowed this to be widely known, was in high regard with the people, always dignified, he spoke Serbian and was always the favorite Serbian Prince as he knew what things Serbian people fall for.