Patriot Paradox
The artistic conventions it broke were basically that back then, rock was rock, folk was folk and complicated lyrics were for operas, not pop songs. This song mixed rock and folk elements and had complex lyrics and still became a hit.
The songs that really had an impact on all the "conventions" that followed . . .
Stairway to Heaven - Zeppelin
Boehemian Rhapsody - Queen
Wish You Were Here - Pink Floyd
Dust in the Wind - Kansas
Goodbye Yellow Brick Road - Elton John
Money - Pink Floyd
Satisfaction - Rolling Stones
Hotel California - Eagles
Shook Me All Night Long - AC/DC
Yesterday - Beatles
Johnny be Good - Chuck Berry
Jailhouse Rock - Elvis
All Along the Watchtower - Jimi Hendrix
Enter Sandman - Metallica
Proud Mary - CCR
Mrs. Robinson - Simon and Garfunkle
Two Out of Three Aint Bad - Meatloaf
Free Bird - Skynyrd
Dream On - Aerosmith
My Generation - The Who
Kashmir - Zeppelin
In the Air Tonight - Phil Collins
Africa - Toto
Learning to Fly - Pink Floyd
Fly Like an Eagle - Steve Miller Band
Every Breath You Take - Police
Immigrant Song - Zeppelin
Sound of Silence - Simon and Garfunkle
Hysteria - Def Leppard
Good Golly, Miss Molly - Little Richard
La Bamba - Richie Valens
A Day in the Life - Beatles
Jeremy - Pearl Jam
Rocket Man - Elton John
Diamonds and Rust - Judas Priest
The list goes on . . .
Because it was long enough for DJs to go to the bathroom
It has a whiny stoned hippy singing nonsensical lyrics ina weird voice that gives another group advertisements. Or else not.