Well I think there is something that links some of the original examples posted by Minty in this thread.
Football - this is almost a religion to some and as country I think far too many people are obsessed by it.
Royalty - as in Diana's death. There are many people who clearly still love or are obsessed with the Royal Family.
So to my mind these two things, football and Royalty both have huge public followings and as a result get a heck of a lot of coverage. So there is some sort of collective body of "fans" for want of a better word that will all react to events that occur to anyone in these spheres en-mass.
I also think there is some self serving bandwagon motive about such things. Soccer "coming together" over the Muamba thing was an opportunity for the fans to paint the game in a good light. A cynical view? Maybe but I bet there is some truth in it.
I myself having no interest whatsoever in soccer and only took a very passing interest in the Muamba situation because it made the headlines and was an unusual situation.
I was more affected by Ian Millward's loss when his son died but even that was probably because I have a son of the same age rather than because of the RL involvement but I suppose I may never even of heard of this had I not been an RL fan as RL people just don't get the same coverage in the national press.
There seems to be some sort of herd mentality when we see such big reactions to certain events. Whether this mentality is now more prominent than it used to be is the question. I think it is. In the past (say 60's and 70's) soccer wasn't the obsession it is today. It was just another game for many whereas now its a religion for many more.
I am trying to think which such "religion" I belong to but I can't really think of one.