And they're doing the same thing tomorrow night, pre-empting NBC's 'White Flag Saturday Night' rerun block with No Way Out, a 1987 Kevin Costner film I don't think Kevin Costner even remembers (remember the Cold War kids?). And they can pack in every political ad their heart desires.
Besides that, WDIV knows the people who really want to check it out will probably Hulu it anyways, and it's highly likely the scheduling was done weeks before when they thought Community and Whitney would be on instead of that.
Also, WDIV pre-empts a lot of things. They and their Houston station as we've said many times here don't care about NBC's late night post Fallon/SNL and completely ignore it all, and hate poker. So this is par for the course for them, but at least they get their community programming requirements filled in somehow with the local Halloween show.