It's the same thing with minimum wage - politicians feel good raising it and for those that remain employed it is a good thing. But it ends up in fewer job opportunities, causing further unemployment.
This looks like a great policy at face value but in the end, it's going to mean many fewer H1B's. This is a win-win for the Trump administration because it looks like they're doing the right thing and perhaps they are, but it's also keeping foreign workers out and providing Americans with more jobs, which is exactly what they want.