Such as...what? What "informed decision" is there to be made?
He doesn't have any obligation to Trump. The obligation would be to the country as a whole in not deliberately disseminating information that will damage our foreign relations. Some of that type of stuff was in those Snowden documents as well - disparaging things about foreign countries/politicians that damaged the U.S. when they were made public.
Apparently, there also was a lot of that kind of stuff in the Hillary Clinton emails as well. Nasty things that were said about various people they dealt with overseas, etc., that would have been damaging to the U.S. (as well as to Hillary personally) if released in unredacted form. Perhaps embarrassing to the sitting Administration as well.
So the question is -- do you think all of those things should have been released in unredacted form, so that both the American people and foreign countries could see exactly what Hillary Clinton and everyone on those email chains thought about various foreign countries, American political leaders, etc..? I mean, since you're talking about the value of making "informed decisions" about our President, shouldn't that logic have applied even more so when the country was trying to decide who would be President for the next four years?
I don't recall anyone really arguing for that.