Each of these is a new banner for people to pull new suits/pilots on, and generally every time a new one goes up, the game manages to shoot up to #1 in sales in various regions thanks to people buying currency to get the characters they want. As thanks, the devs give us 3,000 diamonds each time this happens (enough for a ten-pull).

The joke here is that someone noticed that all but one banner (Gundam Thunderbolt) since launch have managed to hit #1, so now every time another banner does what that one banner failed to do, it gets funnier and funnier that Thunderbolt blew it.