If 100 million sign-ups in five days is losing, I don't want to win.
A better number would be that they were able to push 1 in 40 of Meta's users and 1 in 10 of Instagram's users into the app signup in 5 days of national press coverage. I have no idea what typical uptake of a feature is in Instagram. Nor do I know how many people signed up and checked it out vs. became actual active users.
I also am not sure if 100 million users is even anything to be excited about at Meta's scale. Google seems to kill projects that have that many MAU for lack of executive support.