Why did Lords of Vale swear allegiance to a Northman?

Question

In season 6 episode 10 we saw:

Jon Snow was proclaimed King in the North and everyone present chanted "King in the North" for Jon including the Lords and Knights of the Vale.

This is unusual because:

1. The Vale has always been a distinct Kingdom in Westeros, ruled by House Arryn for centuries.
2. In the past, the Vale and the North were bitter enemies and fought several wars over the islands of Three Sisters for centuries.
3. Valemen are mostly Andal (with a few exceptions like the Royces, Redforts etc.) while Northmen are mostly First Men (with a few exceptions like the Manderlys)
4. Valemen follow the Faith of the Seven while Northmen follow the Old Gods.
5. The Vale's Lord Arryn is cousin of Lady Sansa Stark but he is not related to Jon Snow at all.
6. The Vale has never been ruled by any Northern House while North has never been ruled by a Valeman.

So given all this, the Vale is a distinct region with ethnic, religious, social and historical differences with the North. They do not have any reason to support Jon Snow's bid for sovereignty.

Petyr Baelish may have brought the Lords of the Vale with him in hopes of marrying Sansa and seating her on Throne of Kings of Winter but that hope has gone awry given that Sansa has spurned Baelish's proposal.

Some people may point out that the Riverlords previously did so as well when Robb was proclaimed King in the North, but the Riverlands have never been independent for a long time. Before Aegon the Conqueror came, they were ruled by the Ironborn. The Royal Houses of the Riverlands are extinct, unlike the Vale where House Arryn still rules.

So why would the Lords of the Vale accept the rule of a Stark bastard instead of supporting independence of the Vale in alliance with the North?

Or in case that it is my misunderstanding the Valemen took Jon for their King (it is possible that they may have been just acknowledging Jon's sovereignty on North), is there any evidence that they did not proclaim Jon as their King as well?

EDIT: It has been pointed out that Baelish said he had declared for House Stark so Valemen Aristocrats were right to join the chant. What is not pointed out is that Baelish explicitly told Sansa that she was the future of House Stark. Jon is not a legitimate member of House Stark and was still a bastard. Northmen may have some sentiments of Stark loyalty and revenge for Red Wedding playing for them but that is nothing to Aristocracy of Vale. Why should they suffer a bastard of a Northman to be hailed as King? Why should they kneel before a bastard when they can kneel before their own trueborn Lord who comes from line of Artys Arryn, the Falcon Knight.

Answer 1

Just because the Knights of the Vale chanted "King in the North" doesn't mean that they are submitting to his rule. They might simply be recognising him as literally King of the North (and not The Vale).

In any case, I don't believe that the knights would be accepting a new ruler without the consent (or even presence) of their own lord.

In a scene with Sansa, Lord Baelish tells her that he has declared for the Starks. So, if the lords of the Vale do swear allegiance to a Northman it is in line with the Lord Protector of the Vale and their de facto leader.

Answer 2

Although I believe pajevic's answer is enough, it can be elaborated.

Differences between Robb's and Jon's proclamation

Watching both scenes, there is a huge difference. Lords of the North and Riverlands knelt before Robb Stark. Bending the knee is the accepted form of pledging loyalty. It recurs throughout the entire series/show.

However, when Jon was declared king, only Lord Manderly and Lord Glover explicitly knelt. The rest of the lords of the North and the Vale never knelt. They only chanted "the king in the North" with their swords up in the air. I think Lord Manderly and Glover stood up in this part as well. I do not think this is an acceptable form of pledging fealty. This looks more like recognizing authority. Hence, the lords of the Vale were not offering their swords to Jon Snow. They rather were happy with their newly formed alliance.

Declaring for House Stark

I am not a native speaker, but I am not sure if declaring for does necessarily mean accepting rule. It feels more like accepting Stark rule for Winterfell. There are two sentence examples here, both of which can mean either "accepting its authority over oneself" or "accepting it as a (rightful) authority over some others". However, a native speaker can enlighten us better than me.

Why would lords of Vale be happy about Stark rule?

You suggested Vale was an ancient enemy of the North, however only 20 years ago they toppled one of the greatest dynasties in Planetos. They should be happy that their former ally being ruled by a great leader. Note that Jon became Lord Commander of the Night's Watch at a very young age and proved himself many times.

The death scene of Lysa Arryn does not offer any light on this matter, however according to the books, to fulfill Baelish's request, she resisted the demands of the lords of Vale to join war to help the North. These lords always wanted to help Starks, so they were happy for the well being of the Stark family being protected by a strong leader.

We can even further speculate that the lords of the Vale did not want Lord Baelish to obtain more power. Most of them distrusts Lord Baelish (remember the investigation after Lysa Arryn's death), and at least one of them, Lord Royce, had an open quarrel with him. Maybe they were afraid of Baelish obtaining the power of North via Sansa and Sansa becoming a puppet under Baelish, just like Lord Arryn. To this end, they may have wanted to grab the opportunity provided by Lady Mormont and facilitate the proclamation of Jon Snow as king. Note that no king is king if he is not recognized by others, hence the support of the lords of Vale increased his legitimacy.

In short, Lords of the Vale did not swear allegiance to a Northman, they merely recognized the authority of a Northman only over the North, they cherished a hopefully stable era of the North as an ally.

Some remaining contradictions

With the aforementioned scene, the North declared its independence under Jon Snow's rule and Vale accepted it. Does this mean Vale also declares independence? If North is no longer a vassal ruled by King's Landing, how can Vale, a vassal of King's Landing recognize its independence?

Still, I believe this is the most plausible explanation until further material is provided.

Answer 3

Just to throw in my 0.02€ of knowledge and theory:

Ever since Ned grew up at the Arryn's there appeared to be a very strong bond between the houses. Which of course peaked in Robert's Rebellion, which was also successful.

Lysa was born a Tully. This probably caused the Vale to at least feel a little for Riverrun when the Lannisters came, and before, when Robb's host failed. This also forges another link to the Starks though Catlyn.

Apparently all was well between the North, the Vale and Riverrun for many years. Then came the lunatic Freys, Boltons and the occasional army from the south which all greatly destabilised the entire region. Stories about Ramsay must have reached the Vale. I expect living next to the psychopath's realm with winter coming is quite troublesome.

With Jon's rise to king, which I still believe he will deny, the civil war in the North ended. Jon is almost a Stark and has Sansa at his side, which makes him a more rightful leader than any Boltion ever was. Promising more stability and with a high probability a more sane ruler. Definitely a ruler who is NOT known for flaying people he doesn't like.

Helping Jon and especially Sansa was their mission when they left the Vale and Jon's rise to king is therefore their achievement, after a fashion.

Also they just killed a few towns worth of people so there was probably plenty of adrenalin already. With their alliance they consitute a united power now, with fewer potential fronts and enemys, with a stronger army on the whole. They also have a clear direction now, instead of passively haning in limbo between all the waring houses.

I guess then it was just the heat of the moment where they celebrated their success when they took part in what initially may look like Jon's coronation.

Answer 4

I think they all proclaimed Jon Snow King of the North including the Vale for reason being, it had become known to them that the North needed to unite to fight a common enemy. Jon seemed to be the viable choice being the best fighter and also son to Ned Stark.