That’s not what the poll asked. Wording matters a lot in polls. The question was worded as approval of deporting undocumented people in general - not necessarily of how Trump is conducting it. Quite a number of people have bought into the false the right wing narratives that most undocumented people are [insert negative thing here]. Then when they see brutal operations that don’t reflect that narrative they start to oppose the operations - but not always realize the premise was false. When you poll on how Trump is conducting things, the approval falls a lot more