I've been wondering, with the crisis on Earth after the rocks were dropped and the exodus of people from Mars. Why don't people from Earth move to Mars? They have vacancy to fill and would probably the kind of ironic justice the expanse follows.
I see issues though, first it might be an issue with the bottleneck of people just trying to get off earth and into orbit, second just the general anti earther strerotype on Mars might hold back the Martians to offer up houses for those who are in need on earth, third alot of the ships are going to the planets opened up by the Ring Gate, thus taking away the auxiarally ships that may have contributing to the relocation effort.
Also Im not sure how the Mars is doing on supplies, maybe after all the war efforts, they still need basics like water from the belt, which they might not still be geting, to supply there own population.