I don't think we can avoid it, boxing organization is doing everything they can prior to the fight, test and everything to see how healthy the boxer is. Maybe reducing the rounds again? but it won't be as competitive.
It's inevitable, there will be always some cases like that every once in a while. In the world of combat sports, the risk is always there and safety is not guaranteed, they may try to reduce the risks but they cannot take that factor away. Promoters, organizers, and fighters/boxer know that fact but they still chose to move forward because of the reward that they could get every fight.
That won't happen as per reducing the rounds, there are specific rounding counts depending on the weight limit per se. It's unavoidable really because it's a contact sport.
The boxers are aware of those risks because even a long time ago, they've heard and seen the news about a sudden passing through major blows on the temple.
That's the risk they know and their trainers are also assessing that so that it won't happen to the fighters that they're coaching. They know what's best for each of them and they've already embraced this as a chosen profession.
Yes, the trainers know it beforehand and so with the fighters, and they are all aware and prepare with it though there are precautions that they will practice but accident can happen and if fate allows it can happen with them, the organizations though are doing everything to lessen the chance and they are to be kept in adjusting to make sure that they are complying with safety precautions to avoid having such kind f cases during the fight.
Those few that still encountering coma or to the point that fighter dies after the fight, cases that are unavoidable anymore since before the fight medical and physical test has already been done making sure that both fighters are fit to face their opponents.