They ALL came after the game was over, according to everything I'm reading. The 3 friends arrived just after the game was over (time for celebration!) Then the fifth guy came over somewhat later.
Cocaine *does* help with alertness/acuity. My first study of the drug was among surgical residents and surgeons at a major hospital (and I have interviewed other doctors who specialize in the treatment of cocaine-addicted doctors). Indeed, many of these doctors continued to use under supervision of other doctors (cocaine is, after all, a prescribable drug). It's schedule II.
I don't think the four men watched the game together (they may have watched segments of it that were recorded, of course). I've known many people at parties where they did a bump right before going out the door to drive, actually.
If your theory is right, then the men probably didn't know their coke was laced with fentanyl (in which case it is indeed question about who brought it, when it began to be used, etc - maybe they did several lines of coke at around midnight - and it was laced with tiny amounts of fentanyl - either through cross-contamination by drug dealers packaging and weighing or for some other purpose).
So many weird things to think about - but fentanyl is definitely a major death-dealer in the US.
If so, since it only takes an amount equivalent to a mere 5 grains of salt to produce death (and the weight of that amount if tiny), people must be adding HUGE amounts of fentanyl (but why? why not...cornstarch? arrowroot powder? Like in the good old days? even crushed salt! none of those would be lethal or psychoactive and would be way less expensive and add weight).
I too keep turning that question over and over. So far, I like the addiction theory (get people inadvertently addicted to opiates). Since only some people respond (but respond strongly) to the addictive/high aspects of opiates, they might go back to the same dealer to get the cocaine that suddenly they want even more of, than usual. Maybe it makes people take more lines? Chasing the opiate high?
I really have no clue.