What criteria are used to determine who is band number one? Record sales? Downloads of music files? Sale of tickets for concerts? How many times does the artist's name appear in a web search?
The music industry is completely different from what it used to be and many fans, especially the old-school fanatics, refuse to adopt many of the stupid modern conventions we are asked to respect.
I will not deny that they seem to be popular, their videos have many views and they seem to be a band that is being talked about, but that is because many people do not really know how to look for and find new music. In addition, they simply listen to what is presented to them, what is more readily available and what everyone else is listening to.
They are not number one for me or anyone I know, and I know many people who listen to rock music.