How to explain a career move in an interview
You do not need a rehearsed speech. Be honest about what you have learned, what you want next and why this particular role interests you.
If your current job has frustrations, keep the explanation factual. You can say the travel has grown, progression is limited or you want more involvement in delivery without turning the interview into a complaint session.
Most hiring managers are trying to understand your decision. Give them something clear and fair to work with.