Out of Pod Experience

To use an overused (and usually inappropriately overused) term, chaos theory.
Very slow atmospheric reentry is a "chaotic" process, meaning an extremely complex process with a lot of factors that influence it, where even the slightest change in conditions could potentially cause a drastically different result.

It could take many rotations around the Earth through a very low density atmosphere for the orbit to really start decaying, but once it really starts decaying, it goes very fast.
The problem is, the point where that happens depends even on the most minute changes in high altitude atmospheric density (making the atmospheric micro-breaking fluctuate wildly), so predicting when (and therefore where) it would happen is as good as impossible until shortly before it really starts happening.
And when it really starts happening, it's going to be over very soon.

P.S. Most of the time, we do at least have a rough idea of a narrow band along the orbit where it could come down. We just don't know where along that very long narrow band it will be.

P.P.S. That's why we usually do "controlled re-entries", where we instruct the satellite attitude control drive to start a re-entry burn with all remaining fuel. This almost always results in a fairly predictable crash location. This satellite was one of the few relatively modern ones that were left to their own devices, having used up all its fuel to stay in orbit as long as possible.
It was launched in 2009 in a very low orbit, which was necessary for the type of research it was doing, so it regularly used up quite a bit of fuel to maintain orbit. In order to do a proper controlled re-entry, its mission length would have needed to be considerably shortened on top of its already short lifespan.

maybe played a bit too much Deus Ex, but I can only see FEMA as puppets of bad guys