Because the preposition к normally requires the dative case.
So:
This is a very common pattern in Russian:
So к + dative is the key rule here.
Долгим is the instrumental singular masculine/neuter form of долгий.
Here it is used as part of the predicate after был:
In Russian, after forms of быть (to be), an adjective describing what something was is often put in the instrumental case, especially in standard written Russian.
So:
You may sometimes also see nominative in some contexts, but был долгим is very natural and standard here.
Был is the past tense masculine singular form of быть (to be).
It agrees with путь, which is a masculine singular noun.
Compare:
So the form of быть changes depending on the gender and number of the subject in the past tense.
Стоил is the past tense masculine singular form of стоить.
Here it agrees with the same subject: путь.
So the second clause really means:
Russian often leaves out the repeated subject if it is already clear from context. English can do this too: The trip was long, but was worth it—though English usually prefers to repeat it more explicitly.
Стоить того is a very common Russian expression meaning:
Literally, стоить often means to cost, but in this construction it means to be worth.
Examples:
So in your sentence, но стоил того means but it was worth it.
Because стоить in the sense of to be worth normally takes the genitive case.
The pronoun то changes as follows:
So:
This is a fixed and very common expression. You should learn стоить + genitive as a pattern:
Because но means but, and in Russian it normally connects two clauses here:
Just like in English, a comma is typically used before but when joining two clauses.
So the punctuation is completely standard.
Путь can mean several related things:
In this sentence, it is not just a physical narrow path on the ground. It can refer more broadly to the way to the sea or the journey to the sea.
That is why a natural English translation often uses journey or trip, even though the Russian word is literally closer to path/way.
Yes, it could, but the nuance changes a little.
So:
Both are possible, but путь is a very good choice in this sentence.
Russian often omits words that are easy to understand from context.
The full version would be:
But repeating путь would sound unnecessary. So Russian naturally leaves it out:
English does something similar sometimes, but Russian allows this kind of omission very comfortably when the subject is obvious.
It is natural standard Russian, but it has a slightly literary or elegant feel, especially because of:
It is not old-fashioned or unnatural at all—it just sounds a bit more polished than very casual speech.