Hoping that some of Fringe's DVR/Hulu audience will tune in on less competitive Friday, when they don't on Thursday, is giving Fringe a chance. The Thursday ratings justify cancellation. And if anything Fox has will increase a Friday audience, and it can afford to move away from a high rating night, it's Fringe.
The remark above about moving it to Thursday is what hurt it is true. It had one of Fox's best lead ins, though, and wasn't doing huge business. It was time to see if they Fringe could take its audience elsewhere, and use the lead in to build another property. The audience didn't go to Thursday, hence Fringe's shift to a highly serialized format. (You didn't think that was an artistically motivated decision, right?) Now it has a fanatical following.