it was inevitable that some act or another
would be the first-to-market with catchy
tunes and stadium-filling star power.
This is a profound misunderstanding of how weird and unlikely the Beatles phenomenon was.
Post-WWII acts with catchy tunes and star power were already abundant before the Beatles. They were not special in that regard.
What was unique about the cosmic accident that was the Beatles?
1. Happened to be paired with a (initially reluctant) producer of classical music
2. Achieved worldwide fame and chart dominance (this part is not unique, but its place in the sequence of events is crucial)
3. Somehow this popularity crossed over into the US, the world's largest market, when American response to prior British acts was lukewarm at best
4. After achieving worldwide superstardom, decided to push the boundaries of pop music
5. Conveniently had a producer who could help with and encourage this transformation
6. Decided to give up touring at the height of their fame, to focus exclusively on studio albums, and were able to do this thanks to already having achieved megastardom and financial independence
7. They accomplished all of this in, essentially, a single decade and then called it quits
8. Having three world-class songwriters in one group that started out as a cover band is a very low-probability event. The number of excellent, instantly recognizable, songs that they wrote over a period of 7 years (1963-1970) is insane.
Also relevant was the UK art school system, which up until the 80s or so was a practical career path for creative working class kids.
There was also the dole (unemployment benefit) system which provided just enough cash to allow bands and musicians to start a career without being forced into a full-time job.
A ridiculous number of high profile UK musicians from the 60s and 70s came through art school or adjacent courses like architecture, not music college.
This was a really good answer but I also don't think it invalidates the GP's point. There was a particular set-up at a particular time that meant that pop music was going to go very big and that explains more of The Beatles phenomenal success than your very interesting points do. Your answer explains some of how The Beatles became more than the average pop group but they still ("She loves me, yeah, yeah, yeah") started off as just a (boy band) pop group.
It's She loves _you_, yeah, yeah. Little quirks like that (using second person) set the early Beatles records apart from contemporary boy bands and were a forebode of that they were more than just a boy band.
There was a particular set-up at a particular time that meant that pop music was going to go very big and that explains more of The Beatles phenomenal success than your very interesting points do.
Pop was already big, see Elvis. If The Beatles were not as exceptional as they were, they would have maybe two or three hits and disappear, like most bands of the time. They were exceptional songwriters, who stood relevant for almost a decade, because they infused new ideas (e.g. from avant garde) into pop music. In contrast to e.g. Frank Zappa, they were able to convey these ideas to a large audience.
Around 1969-1970 they started to loose their edge. After a wildly experimental period (~Revolver to Magical Mystery tour) they slowly returned to more conventional Rock & Roll (see e.g. the album Let It Be). If they hadn't broken up in 1970, they would've probably become less relevant after then. E.g. even though McCartney's songwriting was still good in the 70ies, the world had moved on (disco, punk, etc.), with the ex-Beatles becoming less and less relevant. Except perhaps Lennon, who would work with more contemporary artists like Bowie.
GP stated that the Beatles were inevitable, that somebody would have come along with catchy songs and "star power."
That part of the GP's post makes little sense to me. There were plenty of post-WWII (and pre-WWII) popular music stars who fit that description.
Yes, an endless parade of popular music stars was inevitable, but something like the Beatles wasn't. Pop would have evolved with or without them, of course, but their impact was insane.
Post-WWII acts with catchy tunes and star power were already abundant before the Beatles. They were not special in that regard.
What was unique about the cosmic accident that was the Beatles?
1. Happened to be paired with a (initially reluctant) producer of classical music
2. Achieved worldwide fame and chart dominance (this part is not unique, but its place in the sequence of events is crucial)
3. Somehow this popularity crossed over into the US, the world's largest market, when American response to prior British acts was lukewarm at best
4. After achieving worldwide superstardom, decided to push the boundaries of pop music
5. Conveniently had a producer who could help with and encourage this transformation
6. Decided to give up touring at the height of their fame, to focus exclusively on studio albums, and were able to do this thanks to already having achieved megastardom and financial independence
7. They accomplished all of this in, essentially, a single decade and then called it quits