The thing is that even without Owen intervention, Nux would have still died, the main cause is stemmed from him being too angry, that led him to do impulsive shit and get into unwanted accidents. His death rate skyrocketed when he return to Earth and Owen tried to visits Nux and prevent his death in various timelines but failed. This repeated actions of Owen cause a time paradox, which causes the past itself to change drastically, such as Nux existence being erased completely by the laws of universe.
Tldr: Nux is destined to die early and the longest he ever lived is 23 years old, so Owen focused all his resources and time when Nux just start his college so he can live longer.
Thanks for explaining this, I was genuinely kinda lost with the whole time rewind thing
Well, i understand nux feels though. Think about it. Many times you've been died then there's someone keep reviving or turning the time or past to see you again. Just give him a peace. How many times you turned the time, you should know that you are the reason why nux is dead. It's simple solution, don't approach him, moved on so nex can have a peace or lived with his own life even though he's a lot of struggle. JUST LEAVE HIM ALONE, PLEASE