And his replacement was picked by State Department, with the official that was, by the law, supposed to hold the office until elections, stepping down after being told so by American ambassador.
I think the official explanation is that Haitian justice system is in shambles. Unofficial explanation is that this was CIA/SD op and they are making sure they won't talk, either via cushy deal or a permanent solution.
And how would Haiti go to war? They have zero ability to do that. Dominican Republic on the other hand has some capabilities, but doesn't want to have anything with the cesspool they are bordering.