Most of us just want to fit in, and believe what everybody believes.
Coming to your beliefs this way is not actually intelligent. We don’t do it consciously. It’s just tribalism or herding instinct or whatever.
So if everybody agrees with you then that’s a pretty good sign that you are wrong.
I think you’re confusing a few things here, but that’s ok. After all, it’s a shower thought, not a thesis.
Whether people agree or disagree with you is not a good indication of you being right or wrong. it could be either way in both cases.
When people think the same way as you do, they tend to agree with you. They might think that way, because you’re really convincing or because they see the world the same way you do. In either case, you could still be right or wrong.
It’s also possible that people appear to agree with you even though they don’t actually think like you do. See dictatorships for more info on that situation. As usual, this has nothing to with who is right and who is wrong.
Regardless, you touched upon an important point. Humans are social animals, and tribalism causes all sorts of weird behavior, such as rejecting your own conclusions and going with the flow. In a hunter gatherer society, your life literally depends on the group, so you better stick together. In a modern society, we still need each other, but more indirectly.
If everyone agrees with you, take that as a warning sign that they might be acting on tribal instincts. Act responsibly, because your decisions could affect the people around you.