Queen - can someone please explain?

This is an interesting bump. I wonder if @Charlatan still feels so ambivalent? Probably I guess. And honestly people like what they like, I'm not going to try to sell anyone on Queen or any other band. But if you did ask my opinion, it would be that Queen's popularity really just boils down to two things:

1. They were (and are, as appropriate) phenomenal musicians. Freddie of course was a virtuoso singer but also an accomplished pianist. Brian May regularly makes lists of greatest guitarists. Roger Taylor and John Deacon are less celebrated but together made up a super solid rhythm section to lay the foundation on. These four men are all just top class musicians and it shines through even when they're not necessarily doing crazy complicated things. Which is good, because

2. They were accessible. Queen was definitely proto-prog and was doing a lot of experimenting. Their use of the sound stage, huge layered multitrack vocals, lots of effects, all hallmarks of what we would today think of as prog rock. But they knew how to use those elements effectively without overdoing it. Queen songs are just catchy and easy to sing along to, and if you're not really listening you can easily not even notice all of the complexity happening (though I wager you'd notice if it wasn't there).

So, like, that's it. Yes, Freddie Mercury was a top notch performer with unmatched stage presence. Yes, Brian May shreds like a god. Yes, they came at a time when rock was in an evolutionary stage and a lot of different sounds were able to find an audience. But really, honestly? They were super talented people doing really catchy and easy to listen to music. That's pretty much always going to be a winning combination.