Hillary wanted to dramatically expand the H1B program (footnote). Whatever your stance on the issue, you should be able to understand how this upset some American tech workers.

There are similar stories in other sectors. Economic protectionism hasn't really been in either party's platform for a long time, and during that time American workers took a severe beating. Then Trump came along and started making promises.

* More precisely: Tim Kaine proposed a bill to double the size of the H1B program and Hillary has been in bed (donation-wise) with Tata, Wipro, and the like for the last decade at least. When asked for her position, she maintained strategic silence or dodged the question.