Secondly, you don't have to explain anything. Smart hiring managers will understand that you focused your career mastering a craft and that you're still working on that craft you mastered. As for the dumb hiring managers, it's best if you can avoid working for them. One thing you'll learn as you get older is that you can't please everyone all the time and if someone is foolish enough to hold stupid things against you, good riddance to bad rubbish. If you look around a bit, you'll find there's far, far more opportunities for intelligent old coders than unintelligent old managers.