No offense but way too many people can just simply become fighters ever since mma gyms are on every corner, way too many people getting involved for the wrong reasons(ego, clout etc) not saying this guy was or anything.
When this happened there was a few reddit posts about the incident, they were fighters that mostly trained together for a charity event, one of the participants had trained with the deceased before the event and mentioned how he would be gasping for air after a 2 minute drill and everyone noticed it also a red flag was that he appeared to be in amazing shape aesthetically don't want to make any assertions but I think you can draw conclusions for yourself.
After this occurred it got me thinking that other athletes have gotten extremely fatigued in trying mma or bjj, if you think about it when you go all out in a fight you have about 60 seconds before you completely gas out, this is why the best fighters keep distance and read the opponent and pick their strikes if you saw this fight the deceased went all out flailing punches and by the end of the first was completely gassed they needed to give him extra time to recover towards the end of the fight his arms were limp and shortly after he went into cardiac arrest.
Amateur mma seems much more dangerous than pro level, I wonder how much anxiety and nerves play a role into these incidents because that can dramatically increase your BP and heart rate on top of that you're going into what it probably one of the most strenuous experiences its a bad recipe, point is you must be in tip top shape just as a prerequisite then there's your mental state which has to be kept in check as well.