It can get incredibly complicated depending on the artists, recording studios and perhaps most of all the complexity and control of their contracts that bind them all together.
To ponder why they chose to do so, provided it was legally and contractually their choice in the first place. And to also consider that real creativity can't be expected to be bottled up within a single genre. Then again for some musicians, it isn't so much a matter of changing direction as it may be that their own creativity becomes exhausted. All of which doesn't necessarily imply they "sold out".
Though I can also think of a classic example as well. Which was why lead vocalist of Jefferson Starship Grace Slick permanently left the band, that was clearly headed in a more commercial direction that contrasted their original hard-edge rock as "Jefferson Airplane". If you read about them, the phrase "sellout" often pops up.
Historically speaking, in the days before drummer Dave Clark of the Dave Clark Five, recording artists tended to be property owned by record companies. Almost a form of contractual slavery. That much was true. Dave Clark was a true "pioneer" in the industry, being the first musician to aggressively control his intellectual property rights above and beyond the record studios. Which left him incredibly wealthy, and ushered in a new era of independence and prosperity for recording artists.
Even The Beatles Paul McCartney lamented over not owning his own music,or having total control of music being developed in the studio. Yet the evolution of their music was in the minds of most people considered to be brilliant, regardless of a number of persons and entities steering it in different directions. And when they finally gained control of their own music to form Apple Records, it was too late. All four of them wanted to go their own direction as artists, regardless of what the fans- or myself wanted or expected.
Musicians being mostly artists first and perhaps capitalists second. Being under no obligation to pander to what the public wants. Contrasted by recording studios are capitalists first, second and last. Whose primary obligation remains to their directors, officers and shareholders. Not their customers.
