My bet is they are randomly pick one or some threads to join and make posts to increase their activity points.
I think that is not the case here since I checked one of the posters and there was only 1 post that was made, so it does not connect to activity points, and nowadays you do need some merits as well to get promoted in a higher rank, so it doesn't make sense. I don't want to speculate a lot about this team as bumping thread is actually not necessary anymore unless there's an important information that they are tryin to announce.
Trustdice has been here for a while running a signature campaign, I think it's enough for them to ensure people will know about them.
These newbie bumpers, not sure if it's related to them or just a newbie trying to connect themselves to the site.