Change is the only constant. It is no one’s fault the relationship ended.
Why should One give up a dream to please Two?
Think of it from every angle.
One is offered a job Elsewhere and Two doesn’t want to leave Here. If One loses the chance, the resentment will destroy the relationship anyway.
People change, what they believe or want or think changes. When the change is unilateral, the relationship is over. To try to maintain it often leads to anger and pain and arguments so that by the time it is officially over, there is nothing but animosity.
This is the mistake.
When there is change, when there is a movement apart, it can end the relationship, but if one is wise, it can end on a friendly note.