So, there are good explanations as to why they are popular, and not a joke even slightly.
What AdP have done is combined:
- Pop rock using looping tech and really tight percussion / guitar work
- Some very technical playing, especially using microtonal instruments with a 24 tone scale
- A dada-esque aesthetic to make themselves standout
- Created a lore that allows them to preserve some privacy
So, no, the music is not a joke. It's real music, made by musicians that have been performing together since they were ~13 years old (over a decade at this point). If you listened with a critical ear you might realize that many of their pieces are actually satirizing the clichés of pop-rock music. The aesthetic is made to be fun and get attention.
I've written a bit more about them here: The Summer of Angine de Poitrine.
Oh, and FYI—if this is a joke, it's one of the most successful jokes in nearly 20 years. They smashed the attendance record set by Stevie Wonder in 2009 for the Montreal Jazz Festival.