Your question seems quite loaded, but a brief history of caliphates is here if that helps you https://en.wikipedia.org/wiki/Caliphate#History
Didn’t mean for it to be. Or to be honest how to really put it. If you and no sarcasm know how to put it better I will delete and repost?
/Joke Answer (maybe)
If they did it in a Muslim majority country they wouldn’t be noticed and globally talked about. It’s a popularity contest after all.
And actual Muslims will actually reject them because they are not the right kind of Caliphate.I don’t think it has anything to do with making the world notice.
I believe it’s the same reason as why Europe formed the EU or why did the US unify into the United States instead of the colonies staying as separate countries.