Same thing -- people calling for odious thing Y (whgich, unlike odious thing X doesn't get them kicked out of Twitter) would not care to go to Gab with its tiny number of users. Of course Gab would court those who might actually be interested in joining.

Not to say that Gab isn't a cesspool, and Mr. Torba, when he shows up here, appears to be a rather unpleasant character, but Gab being full of bad people is a function not only of Gab being bad by definition, but also of bigger players' policies as well.