The episode "The Woman King" from the re-imagined Battlestar Galactica starts with Sagitaron refugees arriving to Galactica. Why do these refugees exist? Why are they there? Where do they come from? Why do they need to be relocated to Galactica? Why couldn't they have remained in whatever ship they were before? The fleet is losing people right and left. You would think there would be a deficit of people, not a surplus. And you would think that as people died, spaces would be freed up for the "extra" people. So, why would the refugees need to be relocated to Galactica at all? If there is an explanation for all this in the episode, I missed it.
It is not just Sagitaron refugees, but these are mentioned as being singled out
For murder by the doctor.
The refugees are people that ended up on Galactica either during or immediately after the evacuation from New Caprica because of a shortage of space in the fleet. It can be assumed that not all the ships were able to be taken from New Caprica as some were dismantled for lodging and other resources during the colonisation, plus several larger ships were
blown up by a nuke detonated by one of the sixes, which is what led the cylons to New Caprica in the first place.
This reduced the available space even further.
If I remember correctly, the decision to lodge the refugees in the spare landing bay (which BTW was referred to as Dogsville) wasn’t directly referenced in an episode but was talked about in one of the “previously on...” re-caps, perhaps showing a deleted scene. This is something BSG did a few times during its run and it always pays to watch those re-caps because they do sometimes fill in minor plot points like this.