So you’re conflating two separate things. Sanctuary Cities are cities that have official policies in place prohibiting cooperation between local authorities and federal immigration enforcers. These have existed for quite a while. Some racist state governors and federal authorities decided “well if you like immigrants so much have some more” and started illegally rounding up immigrants in their cities, lying about destination, ignoring federal laws, and bussing these immigrants to cities that declared themselves to be Sanctuary Cities. Those cities responded appropriately and took care of the immigrants foisted upon them. Of note, these forced relocations occured with little notice to legal teams, meaning some immigrants were shipped multiple states away and missed important immigration court appointments.