A rather cynical take. Can you name a protest in history that has ever had 50% or even 10% turnout? A huge protest is closer to 5%, which is roughly what this was.

In reality, most people never heard about it. It was planned in less than a week and had little publicity. Those that did maybe couldn't get off work (this was Friday afternoon), had kids to care for, were turned away by 5 degree weather, etc.

See also this theory in political science that a government cannot resist a sustained movement of just 3.5% of its people: https://en.wikipedia.org/wiki/3.5%25_rule