Here’s a fun post from reddit:
I believe critical mass is 5%. Once 95% see 5% of the population doing something, they mimic the behavior.
LTNS, Lucy!
To that notion (you imported from Reddit), I'd say "it depends." I'll give 5% as a minimum level. I figure critical mass is a variable amount, depending on who the early adopters are, and how "attractive" the belief or behavior is.
Q has mentioned, "they thought you would follow the stars." Pop culture has more power, probably by definition, "popular." A small number of adopters there will bring along more of the public.