Ghia, your 'rules' for the present perfect are not correct, sorry.
It means his popularity is higher NOW than before (there was a change because of something he did). This is being reported as news so the present perfect is good because it focuses on 'something has changed!' The simple past talks about a past time, so it's not exciting like that.
eg: Juan broke up with his girlfriend a few days ago. = just information.
Hey, guess what, Juan has broken up with his girlfriend! = exciting news = 'Now Juan is single!'