It makes sense if you view it as an intentional effort to demonize the US. Terrorizing visiting tourists is a great way to get the “we are crazy, your best never come here” message out.
The simplest explanation is that this administration wants the US to be hated and sees atrocities as an important tool in that effort.
That department -- customs and border enforcement -- needs to be ideologically pure for the next phase. They'll need to be able to rapidly judge new hires for culture-fit. Can you do the things that only make sense if your boss wants USA to be hated? Can you deftly talk that group of travelers into all unlocking their phones for imaging?
Off the top of my head, playing Devil's advocate it could be to encourage illegal immigrants to self-deport. The jailing of Germans with green cards for a fortnight is an unintended side-effect of cranking up the overall hostility level.
The simplest explanation is that this administration wants the US to be hated and sees atrocities as an important tool in that effort.