Team Evil is the goal of the Empire. The backstabbing is when human nature gets in the way. So really the leaders should promote Team Evil and the subs should look to backstab and conspire.
I guess those subs feel towing the line is less risky way to get to leadership than to conspire.

But The complete lack of Empire imms over the past 3 years or so has made this unclear. It might be worth risking anathema from your boss if there was an actual empire imm around as a possible safety net.