Of course, people can be naive.
It’s very simple, when we figure out the hustle, we are no longer ignorant to that hustle. We no longer have any reason to trust the liars other than our bias is so directed at the liar, for whatever philosophical reasons, that we choose to support the lie.
You don’t call someone stupid just because you disagree with them.
I know I can be hustled, happened many times. I believe in trust, but verify.
If you realize that you can be hustled then you are not stupid. I was getting from you that you considered your self too aware to be hustled. And that kind of person is a prime mark. Find out what their belief system is, play into it and they will follow you like a little lamb.
Afterwards they might see what happened or they might not. Most of us don't like to think we are stupid or easily led.
The most effective and painful hustle is when it comes from family or friends. You are blind sided because you trust.