I didn't really pay attention to the story that much, but I believe his nomad clan was destroyed or he was permanently exiled (something like that).
Yeah, his clan sold out to a corporation, so he left the clan. V even uses the story of his clan as a warning to the Aldecaldo leader Saul not to repeat that mistake. There is always some sort of an excuse for V to be as disconnected from the world as the player is. Because, you see, "V is your character". That's the lame excuse we are to believe.
It's a pathetic and sad moment when a writer lies to the audience that he is doing something for story reasons while he is doing it for reasons of economy and to reduce the amount of work he needs to do on backstory and actual worldbuilding.
The end result is that while Geralt is the competent guide introducing the world to the player, in CP77 the player and the main character being both unfamiliar with the world, always end up needing an NPC guide - another disgusting trick. First it's Jackie, then Takemura and Judy are entrusted with introducing the player to the rules of the world. All this twisting and stretching of common sense for the dubious advantage of being able to say "our character is a blank slate"...
IMO a blank slate main character in an RPG works only as well as the opportunities for the player to fill out that blank slate are present. And for one reason or another CP77 lacks such opportunities. You barely have any quest C&C, interactivity between quests doesn't exist, at least on more than token level, the build system doesn't do anything to flesh out your character strong and weak suits - you are awesome at everything by default, you can't visually customize your looks except in the inventory screen via clothes, you can't see how your character reacts, gesticulates, all the weight falls on the shoulders of the voice actor.
I get the overall impression that for a game that serves you the marketing pitch that it focuses very much on the player's immersion in the role of his main character, Cyberpunk 2077 does awfully little in practice to enhance that feeling of immersion.