Imagine there is a theory, called X. Five years ago "liking" X was unpopular. But today, X is popular. So, a lot of people now are liking X. If X was not popular today, these same people would not publicly like X, just as they were voiceless concerning X five, maybe ten years ago.
The "spiral of silence" explains this behavior. "The spiral of silence counts among the most cited and replicated theories in social sciences." (Here.)
The theory of the spiral of silence can be broken down into the following core hypotheses (Ib.):