The legend goes that Wilson worked himself to the bone making Pet Sounds in response to the Beatles' Rubber Soul. Today neither album sounds crazily different from what preceded it, but at the time they were both big leaps. Fun, fluffy pop marked both bands' careers in the early 60s, but Rubber Soul was richer, folkier, more varied, more album-like, even a little experimental at times. Pet Sounds tried to mimic these qualities in its own way.
Rubber Soul happened at the end of 1965. The Beach Boys released Pet Sounds in 1966. Yay! Totally worth it!
And then, in 1967, the Beatles made Sgt. Pepper's Lonely Hearts Club Band.
And Brian Wilson had a total nervous breakdown.
I'm not kidding. Wilson's mental health was pretty fragile throughout the mid-sixties, but evidently Sgt. Pepper was the breaking point. McCartney has said that the band was inspired by Pet Sounds to make Sgt. Pepper, which is nice and all, but, um...Sgt. Pepper. Your argument is invalid. The Beach Boys were never the same; Wilson went somewhat AWOL until the early 70s, and they kind of bounced back later, but it wasn't like before.
I think it broke Wilson that the Beatles were revolutionizing pop music pretty much right under his nose. He probably had, in greater abundance, the same feeling I have about Randall Munroe (the creator of xkcd), which is like "I totally hate you for your brilliance, but please don't stop making art, but you're making all of us look bad, but I love you, but I also hate you." (Don't misunderstand - I am a little ant trying to make little ant art, and Munroe's had enormous, widespread success, and anyway he and I aren't even in the same field. So it's definitely not the same thing. But that IhateyouIloveyouIhateyouIloveyou feeling's gotta be the same.)
Like this. Remember this? In Ratatouille? When Skinner eats the ratatouille at the end, and is immediately astonished/in love/furious?
So, there we are. Poor Brian Wilson.
But this is another reason why spite and envy about the creative works and/or success of other writers is such a waste of time. If they're better than you, even if they're on another plane of better than you, there isn't much you can do about it but be the best Salieri you can be. History will roll on with or without you; you can't control it. And, after all, Pet Sounds is a really good record. Well worth a listen.