Mmm, I'm not sure of your motives here really OP.
Are you actually asking a genuine question about why people get upset when something happens to a celebrity that they like?
Or is this just another way to have a pop at an establishment that you object to?
Because with your references to privilege and money, plus your later comments on this post, it really does feel like the latter.
Also, I notice that lots of PP who are strongly agreeing with you are also voicing similar distaste for the monarchy.
I'm not someone who has ever, even as a teenager, been prone to outpourings of emotion. I was never fanatical about bands. I don't really follow entertainment news. I certainly am not slavishly devoted to anyone because they're in the public eye. And I mention all this just to underline the point that I'm not defending my own actions here.
I remember working with a woman when Diana died. She was genuinely distraught. She cried at work about it, and she went to lay flowers. A lot of people thought she was a bit OTT but she did genuinely experience those emotions. She had DC, young boys, and she had also lost her own mother when young, so I think the tragedy brought up very raw emotions in her.
If you are legitimately and honestly asking why people get so caught up, then it's not a straightforward answer. There are so many possible reasons.
Let's use Catherine and her announcement as an example. Reasons people might be upset:
Maybe they have young children of their own and can't imagine having to tell them that their mum has cancer.
Maybe they lost their own mum at a young age.
Maybe someone close to them has cancer right now/maybe they just lost someone to cancer
Maybe they're a royalist and are caught in the whole Catherine/William/Harry/Meghan shenanigans and feel protective of Catherine.
Maybe they've followed royal news for years and feel a sense of familiarity with Catherine and her family. I think it's called parasocial bonding. Particularly now in the age of social media when so much information is constantly sprayed around, it's not difficult to feel as if you "know" someone, even while at the same time on a rational level, you are aware that they are just a stranger. Humans naturally yearn for connections, and when you've seen someone for years, like Catherine, it's not unusual to feel some level of emotion - even though the intensity of that emotion may be very variable!
Some people are just really empathic and emotional. That might be annoying to you but it's genuine and just how they are.
And of course, for some people the outpouring might be performative. A way of inserting themselves into someone else's news for attention.
That's just off the top of my head. There are probably tons of other reasons.
I find the people mocking others for feeling emotional are a bit sneery and judgey, and typically there's another agenda such as being anti-royal, or (commonly on MN) pro-Meghan and anti-Catherine. It seems to be on these types of issues everything has to be binary - if you like/support one side you must use any opportunity to attack the other. It's just shit tbh.
I think it's fine to be a bit bewildered by why others feel such strong emotions, but some of the comments on this thread are just deliberately mean.
Bear in mind I'm autistic and spend most of my life trying to work out why the fuck people act the way they do 😅