Or a little bit of both. I certainly think it was planned out to a good extent. Way too many stars have to line up in a bad way for Holly for it not to have been planned out. At the same time, I think the perp was also extremely lucky, particularly in LE's initial handling. My perception is that it was a circus with the inmates running the asylum with no clear leader making clear decisions on what needs to be done or not done.
Yes, imagine if no one had called LE. The Bobo's would have come home that day and seen Holly's car and no Holly. The trail would be at least 8 hours old.
More importantly, I think the fact that it was witnessed really put this case over many others- in a spotlight. Look, we are talking about it here- when there are many cases that only have a few dozen postings and one thread. And still, despite all the attention, the case is still unsolved. Pretty lucky for the perp.