Bush started the use of drones in war, but Obama bears the blame for them in my opinion, because he could have backed away from it but instead he doubled down. I would say the same for the treatment of refugees at the border. Obama built the cages, but Trump uses them with a sickening joy and enthusiasm.
The exception was some misaligned activists that accidentally posted Obama-era photos of "caged" children (behind a fence) a couple weeks early, which happened before some lawsuit forced the feds to release the children instead of housing them with their parents.
Sorry, no I am actually super upset about the ongoing detention and inhumane treatment of people at the border. ALSO about family separation, but the cages are immoral to me as well. Many of these people are not "illegal aliens" but people seeking asylum which is NOT illegal.