Unfortunately, violence often accompanies betting on big money. And in large competitions, such as the championship, there will be large amounts of money on the bets. I'm not talking about possible manipulations here. Let's assume that everything will be completely clean. But someone's oversight (such as the OP mentioned) can provoke an outbreak of violence against an athlete. Which is also understandable - a person who has lost a lot of money will think that it was manipulation, and nothing can prove the opposite to him. So, I don't think anything changes with time.
Well, I might not want to completely agree that nothing changed with time, of course something does change with time even if it appears to be insignificant at the moment, example of that changes is that with what has happened to other athletes in previous times, athlete of this days learn to hide themselves from the fans and the general public when ever they've messed up and sense that fans are not happy with him or her.
And secondly, with past experiences, it's a no brainer that every leagues and organizers will or must have enacted rules that will help protect athletes from attack from fans who are the bettors..
Aside from the above, i agree with everything else you've said, it is often the betting of big money that brings about violence to athletes, most bettors bet an amount they can't afford to lose, and if by any error from an athlete, they end up losing, such bettors want to attack the athlete in retaliation.