Not just being able to change their minds but also to speak about it publicly. I'm sure plenty more have changed their minds but are afraid to speak up because they're afraid it will ding their popularity or cost them votes.

It actually is important. Let me try to explain: the way he phrases it is is as though he needed some internal level to be crossed before he would change his mind. Even though he is way out of his area of expertise. He should have said instead "I didn't know what I was talking about". That way others who also don't know what they are talking about (see some of the commenters in this thread) might take the hint that this isn't about your personal standards for facts, it is about the scientists who have devoted their lives to this subject whose standards apply.

So he could have done a better job on the retraction.

He spent a lot of time and effort working against people who were working to promote climate change and mitigate its effects. Years, articles, TV shows. And he dismisses all of that with a “eh, guess I was wrong, still their fault”.

He hasn’t spent nearly the effort trying to correct his mistake that he spent making it.