Threshold thinking. This is the theory that all humans think socially, they have a threshold number of other people who need to think the same thing before they will commit to believing it.

The threshold varies person to person. Within an individual it varies by subject. It can even vary by time of day or mood. The number changes but it is always still there secretly guiding people's thinking without them knowing.

The threshold can be 0 for a specific time, place, subject, and individual. Someone has to be first for everything that has ever been done.

A low threshold person will adopt new ideas easily. A high threshold person needs a lot of social confirmation before changing their mind.

This is everywhere once you see it. Ever read product reviews before buying something?