As i remember, at the time, the drop in distence to 12 rounds was sold on the basis of safety, when fighters fighting for a shorter distence, - but at a faster pace - would not really make any inroads into safety, fighters going 15 rounds often paced and had "quite Rounds" so this was not appreciably any more dangerous, As Ever, mismatches, Undertrained Fighters, Slow Ref's and Cornermen add to the ever constant dangers of the sport - whatever the distence As i recall the main "Behind the scenes" influance in going to 12 Rounds was the TV companys, they found that they could broadcast a 12 Rounder, with Expert Panelists previewing, in a 60 Minute Slot - 15 Rounders were rather messy for the Broadcast Schedules to accomodate, the catered for additional 3 rounds and minutes rest periods etc eating into the next Programme Slot.
Deaths are extremely rare and are actually more common in college football (and motorsports) than they are in boxing. What happened to Deuk Koo Kim is a tragedy and part of the reason I never give fighters **** for quitting on their stools.