Copying my comment from below:
Please note that an "active user" is an active address( i.e one that has made a bet on the platform) in the past day. This doesn't take into account users that made a bet in the past( most bets have long term horizons, >4 to 5 months) or users that have a current position but aren't betting anymore or users simply observing the markets( looking at a front end like predictions.global)
Also note that active users is probably not a great metric for this application, as it's not a consumer app/ time sink thing.
Money at stake is much a better metric