Why would Epic spite MS or Nintendo?
Could have to do with PUBG and it's deal with MS since it's competition, and this negative press being backed by MS and Nin. While for some people this seems like PS is the only one in trouble, for others like myself, it means Epic is in more trouble than PS. If this negative press leads to MS and Nin gamers boycotting Fortnite at some level, then it wouldn't be a dumb idea for Epic to strengthen their locked down player base on PS4 to make up for those losses. There have also been rumors of PUBG coming to Switch, so all the more reason for Epic to perhaps double down on PS4 since PUBG doesn't and may never exist on that platform.
So now customers should be held responsible for companies being dicks? They should decide what console they buy based on market share? Come on, that's straight bs. Yes, people buying a lot of PS4s created the circumstance, but assigning RESPONSIBILITY to them - and thus taking some AWAY from Sony - would suggest consumers had an intention behind their actions to create this circumstance rather than just buying what they liked. A "guilty mind" to go back to the earlier - and inaccurate - crime analogy.
Also, you are conflating correlation with causation. Implying that Sony HAD to do this, that it was inevitable and foreseeable, if they achieved a high market share. Which is nonsense, this is a choice made by Sony. Not just an inevitable end result of a chain reaction set into motion by outside factors.
That 27%, is also the reason that XB has become super pro consumer in comparison to the start of the gen, as well as Nin becoming more pro consumer as well. To say that those consumers had this intention when they bought a PS4, also then means that PS had this intention the entire time as well, yet why wasn't it present at launch then? It would be like saying XB customers had the intention of buying an XB1 knowing BC and CP were coming, yet they most certainly didn't, and XB may not even have known themselves. The consumers of both platforms unknowingly led to some anti consumer and pro consumer tactics, but that doesn't take all responsibility away from them. Saying as a human being I have no reason to think of the future consequences for anything I do and shouldn't be held responsible, is asking for a world full of chaos.
If you are going for the source of the blame, I guess you could go back to the PS4 launch and say it was PS that offered the better platform which has led to their higher market share. You could also say while PS had the better platform, it was XB who basically screwed their platform up so bad that it seemed like a no brainer to buy the PS4. So is it the fault of PS then or XB? I would say in this case if you had to divvy it up, at the very least it was XB who is 60% the cause and PS 40%.
If you don't want to go that far back, and stick with the more recent year that battle royale has been a big deal on console, then if you want to divvy that up, you could say it's maybe 20% the consumers fault for over buying PS4's, 20% PS's fault for having a larger user base and being to greedy, 20% Epic's fault for being to greedy or spineless, 20% XB's fault for keeping PUBG off of PS4 and having a smaller user base, and 20% Nin's fault for launching Switch so late into this gen and not pushing to get Fortnite on their platform sooner.
You can slice it up however you like, but in reality, what led to this issue is much more in depth than most would like to admit.