That's neat and all, but I will be incredibly surprised if even a tiny fraction of those players are still playing it in 6 years (which is how long DRG has been around). I haven't played Survivor, but the reviews don't really paint it in a super good light, compared to other similar games... claims that the upgrades are uninteresting and there's not much to differentiate the characters and the balance feels off... Early access problems, hopefully, but we're talking about player counts for an early access game, so that's what we've got to work with. It seems like it's just riding on the coattails of the DRG name, for the most part. If you compare it to the player counts for other similar games, it's doing surprisingly well out of the gate, yet reviews ~10-15% poorer than those other entries did at the same point in their life cycle, which suggests maybe it's being bought for the name, not the gameplay.
It's funny that they call out the lower price as being what's drawing people, because $10 is actually on the high end for 'bullet heaven' games. Most drop in the $3-$8 range.
Anyway, point I'm trying to make is that they're comparing apples to oranges, these oranges just happen to have been marketed very well to apple fans.