These corporations are huge, with many many employees (over 30 thousand just at Goldman Sachs).
Just because you used to work for Goldman in the past, does not mean you are a current and future supporter of Goldman.
Nor does it mean that you are a bad person.
Trump is hiring people that know how these companies work from the inside-out. Which is the exact type of person you need to be able to deal with these companies head-on.