Sergey Brin also comes to mind. Unique name, people don't really say "Brin". Just Sergey, given the correct context.
I don't think this is a case of people thinking they're "best buds with the man," like when people rarely referred to Jobs as "Steve."
I hear a lot of people say 'Rishi' now, and it seems to be a bit of a joke at Rishi Sunaks expense, to be derogatory about the PM, rather than branding.
Elon is even more unique of a name to western ears, so I was just pointing out that another (yet less unique) name also gets the first-name treatment.
For more examples, I'd say Satya Nadella also gets 50/50 first/last name treatment in casual conversation.
In India last name could mean anything ranging your "caste" / religion / community / god / place / family / fathers name / or any other random stuff.
Singh is a common last name and if you go to some parts and call Mr. Singh and possibly 100's would respond. And there are people with surname "Bangalore" because they were born there.
And in my part of South India, some of our last name is "First name" of our parents (mostly Father.. nowadays people also started adding their mother's first name). So my name is "My first name" + "My father's first name. And my son is named "Son's first name" + "My First name". It continues this way.
So most of us use the First name to mention someone. And you can see many Indian's making the mistake of addressing some one as "Mr. First name" though the proper usage is "Mr. Last name".
I had this difficulty when in Germany a government office asked why I have a different surname from my kid's and I had a hard time explaining it :)