The break did seem, as others have noted, pretty unusual until you noted the steerer was butted / reinforced. That latter makes me think 'inherent stress riser' and also makes me wonder just how hard a life your Santana may have led before you acquired it.

Of course, I'm also reminded of this posting back in December where you originally identified the fork as feeling sloppy...

So, now I'm curious. Did you ever pull the fork to inspect it or contact Santana to get the service history on that vintage fork?