There is a fantastic German word:

Wendehals (plural: Wendehälse)
literally turn-around-head

Meant are those who after the German reunification turned their stances and grabbed the (monetary/power) opportunities without any moral constraints.

Such behavior is bad. However, not being able to declare a past decision as an error (either because you made an error or because things changed or where unknown to you) is worse.
Unfortunately being stubborn is often praised when it comes to decisions :(