Diversions happen, and the delays caused as a consequence are inevitable to varying degrees. Sometimes a plan is formulated that for any number of reasons fails to come to fruition, thereby adding to the delay. However there comes a point when it is painfully obvious that something needs to be done imminently.
This was a domestic flight landing at a domestic airport. There is no screening requirement for passengers leaving such a flight, nor is there any immigration or customs requirement. If the passengers couldn't be accomodated in the terminal on a short term basis, and they couldn't be re-boarded in any event due to the lack of facility, then there was clearly no other option than to accomodate them overnight or redirect them by other means of transport.
This should have fallen to the carriers relevant operations department in the first instance. Failing that the Commander of the flight should have liased with the local handling agent (if there was one) or directly with his own operations department to put the necessary arrangments in place.
For whatever reason this wasn't done, it was clearly a monumental screw up, and one that is attracting publicity because it is so rare. Undoubtably the costs now will far exceed that of a few hotel rooms and a few taxi cabs.
This is often what happens when you have people in charge who either cannot make a decision, or are too timid to make the right one!