Compromising of one's morality, integrity, or principles for personal gain
"Selling out", or "sold out" in the past tense, is a common expression for the compromising of a person's integrity, morality, authenticity, or principles by forgoing the long-term benefits of a collective or group in exchange for personal gain, such as money or power. In terms of music or art, selling out is associated with attempts to tailor material to a mainstream or commercial audience. For example, a musician who alters their material to encompass a wider audience, and in turn generates greater revenue, may be labeled by fans who pre-date the change as a "sellout".
https://en.wikipedia.org/wiki/Selling_out