This is not a vice reserved for the powerful. Politicians and whatnot certainly do nakedly make a principled argument one and the opposite the next. So does almost everyone. We do it especially when something is at stake, but we'll also do it to win an argument.
It's an irony of human nature. OOH, we're seekers of patterns, principles and consistency. OTOH, we're also highly adept at using these tendencies selectively and disingenuously.
Consistency might happen for a stretch, even a long one, but the first principle is to keep and acquire power.
The people who don’t prioritize power above all don’t hold office long because they lose out to people who do