It's not only "Duelbits" make like this event, example "FJ" sometimes created the same things.

It's for awareness + casinos can get free marketing because the chance is really small. IMO, duelbits user still not can't be same like Stake while they have so many user and income in a short time. 1M$ it's a big chunk, so they make type like this.

Also, to be honest in March there is no special day at all. So, prize pools like this is suitable unless like Christmast or New Years.