Because American citizens weren't being detained? Because people who have legal status weren't being detained at their immigration check-ins and deported? Because government agents weren't ramming their cars into the cars of people they were trying to intimidate or capture, and then lie about what happened? Because agents of the state didn't wear masks and properly identified themselves to members of the public? Because people didn't feel like they needed to always keep their papers on them? Because they weren't shooting protesting priests with pepper balls? Because people weren't being deported to countries they have no connection to? Because we weren't sending people to rot in foreign prisons? Because there wasn't a clear pattern of lawlessness, abuse, lies, and coverups?
Maybe that's why people didn't seriously call it the Gestapo. Maybe that's why there was plenty of criticism concerning Obama and his immigration policies (and Biden's!) but not mass protests. Maybe a difference of degree actually fucking matters.