So what brings this about more in some people than others?
So, as I understand it, it isn't really that some people are more vulnerable to it than others - as you say, everyone is. What we are seeing is many people struck by it on the same topic.
...I have changed my mind about many significant things over the years, and it has not caused even a minor identity crisis for me. Is there a root cause or other signs that signals this tendency?
The first question to ask is how deeply those things really mattered to you. The second question is how many other things were linked to it that also really mattered to you. The third is how many decisions have you made based on those items that you'd regret if you change your mind.
Like, if you were a dedicated iPhone person for years, you might resist the idea that Android phones are better. And, sure, you're bought into the Apple sphere of influence on many apps and services, and changing would be a hassle. But, you know, changing just means a different phone, different apps. There's no real consequence for your prior choice, or changing. So, you might just change your mind, and find Android to be better.
But, if you've been listening to Some News for six years, and they told you covid was a hoax and to not get vaxxed. They also told you a lot of other things, though, that you bought into. And, well, if you came to change your mind, that probably means that some of your voting choices actually hurt people who didn't deserve it....
What's easier at that point - Changing your mind, or sticking your fingers in your ears and loudly singing, "LALALALALA! I AM NOT LISTENING!!!1!"?