oviano: I should have been less cryptic. Sorry.
There was nothing "sudden" about their progress in the search. This search has been going on for over a month. We in the public are not priviy to all of the details of what they consider, what they reject, and what their cueing and trigger information have been.
Part of what they are doing involves the process of elimination, and making the most of such clues as are available. If we let the
drama infested media influence our understanding of this search, we can fall into the trap of assigning traits like 'sudden' to events that unfolded over time for the search team and various national authorities.
They were indeed searching huge areas, but the areas have been shrinking every few days. Nothing strange, nothing sudden.
What took a lot of people by surprise (myself included) was the public announcenment that the early searches in the South China Sea and Malucca Straits needed to be abandoned, and a search far off the coast of Australia in the middle of nowhere granted precedence.
As I understand the background of this search, the indicators that this was a better course of action did not arrive suddenly, but were derived from the process of vetting and analyzing the sparse information available. No drama: plodding detective work.