People who play the "it's my sense of ethics" card instead of the dozen or so other reasonable explanations are so full of

that it's coming out of both ears. It boils down to the fact that they are loudmouths who love to criticize and second guess others but they can't handle that same scrutiny when it's directed toward them. It's easy to have all the answers when you have none of the responsibility.
And in your case, you admitted that you looked the other way when in the presence of all sorts of management dishonesty and crime when you could have done something about it. It's not surprising that you had a chance to step up and chose instead to be an enabling biznitch. It's not your ethics that kept you out of management, it was your lack of a backbone.
I acted whenever I could to stop abusive management, but since it's a rigged system, you do what you can when you can, as in protecting yourself with documented dirt on falsification, unethical behavior etc.
The classic FedEx manager rants and raves and threatens, kind of like you right now. My way or the highway, because that's "policy".
FedEx management is a step down into the sewer, not "stepping up". There's no fixing a system as badly broken as Express management, but since you're complicit and in agreement with it, you're OK with it, despite the many bad actors and inconsistent and unfair discipline.
Express is on the cusp of failure, and poor management is a big part of why they're going down. The courier of today is about half as effective and productive as in the distant past, and the revolving door of personnel and poor service can be blamed directly on a company that is cheap, regressive, and punitive towards workers.
Better polish up that resume, Dano. You're going to need it. Most progressive companies don't want "platoon leader" managers like you who have no idea how to deal with people effectively.
Perhaps you're still young enough to enlist.