They do that because their policies are unpopular and they would lose power if most people voted. That’s why these videos matter: it’s probably not going to convince the MAGA diehards to recant but they’re shocking enough that anyone more patriotic than that might realize that this is far more than normal politics.
The folks I know who were previously sympathetic the constraints on government overreach watched state and federal governments impose policies that made no sense for their communities and were actively detrimental to their livelihoods and enforce those policies with fines and even jail time in some instances.
These people would have been against the tactics ICE is using in 2019. Today they’re ambivalent. The attitude is “what comes around goes around.”