“But if he can order that, why can’t he order an investigation of Hillary”
who says he hasn’t? these kinds of investigations can take a VERY long time, ESPECIALLY to develop a bullet-proof case in court. Nothing would be worse than to bring a case like this and then lose before a jury, because the acquitted crook would then proclaim to high heaven that they had been declared “innocent”, and that the unsuccessful prosecution was nothing but a political witch hunt.
Trump’s own DOJ has refused to undertake investigations of Hitlery or of the IRS scandal. Ultimately, I think this comes down to the President. Tell them you want it done.