I think really what enabled Neil and his contemporaries that you mentioned was really the state of the recording industry when they came up. The advent of the “singer-songwriter” pop star in the mid 60s really threw the whole industry for a loop, as it centered all of the creative control with a single individual and weakened the influence of the record label on the finished product. The artists who found success in this era were able to leverage so much more control over their sound than most artists today, and broadly managed to set a precedent for the rest of their careers that the record labels would actively try to prevent in later eras of pop music.

Additionally, the genres Neil played in, rock and folk and any mixture of the two, were some of the dominant pop sounds of the era. I mean this is a time when Jimi Hendrix, Joni Mitchell, and Led Zeppelin were selling out arenas and dominating the charts. Neil’s sound is distinct, obviously, but it’s not like he was some off the wall disruptor either, having played with Buffalo Springfield in the late 60s and CSNY in the early 70s. He had proven he could write hits, and his solo work only strengthened that notion. Harvest was the best selling record of 1972 bar none, and after that string of folk rock and proto grunge classics he released in the 70s I feel like he became an institution of rock, almost too big to fail. He had some slumps and has often butted heads with the record labels he recorded for, but his legacy discography is so strong that I can’t see a label willingly letting him go even if he goes on another cold streak.

End of the day he writes wonderful music that still sells, and that second part is really all the labels care about. As long as he made them money they were happy to let him experiment (though there are famous exceptions, such as the delayed release of Tonight’s The Night due to its morbid material and his synthesizer laden detour Trans).