The inmarsat pings are/were a red herring. The plane crashed close to last radar contact where there are two or more plausible eyewitnesses. Sailor, drilling rig operator, fisherman.
There also is seismic data and underwater sound sensor data suggesting impact far further nirth than the current s3arch area. Then you have a sighting in maldives as well as a recovered fire bottle. Yes a fire bottle, not some diving apparatus.
For the theories of an ex-NSA guy, check out http://www.jimstonefreelance.com/flight370condensed.html