Cognitive bias
Bandwagon Effect
Believe something is more likely to be true because a lot of other people believe it.
Whether the claim is actually trueHow many other people believe it
Believe something is more likely to be true because a lot of other people believe it.
Example
"Millions of people can't be wrong, this stock is definitely going to keep rising."
Popularity and truth are different things. A belief can be widespread and still wrong, and a belief can be true while almost nobody holds it yet.
The bandwagon effect uses the size of a crowd as a stand-in for evidence, which feels reassuring but proves nothing about whether the underlying claim is correct.
Ask what the actual evidence for the claim is, separate from how many people currently agree with it.