[maxerickson]

Simple explanation is that most people don't have principles.

[interfixus]

Simpler and probably better explanation: We don't all have principles neatly aligned.

Your principle going out the window may be me expressing a deeply held opinion.

[maxerickson]

Well, I would agree that many people treat self interest as a principle. I don't think many people have principles beyond that though.

Maybe mild preferences.

[interfixus]

Most people I know have fairly decent work ethics, standards how to treat other people, honesty up to a point.

Not that I don't share a large part of your cynicism.