"The only way we'll get to understand that is by finding the black box which of course would explain the whole thing anyway."I appreciate that there are technical challenges and costs associated with the following idea, but it would be quite an interesting project to create a system that would transmit Flight Data Recorder (FDR) information to a ground location.
Off the top of my head, it would need to be flexible, perhaps recording more detailed telemetry in cases where cellular networks were available, to being able to provide critical, but perhaps less-detailed telemetry, in cases where only satellite communications were available. In addition, data monitoring systems could be programmed with the intelligence to transmit more detailed telemetry in the event of an anomaly (e.g., the "left turn" with regard to MH370). This would be an attempt to find the right balance of data fidelity, with regard to available transmission capabilities and associated costs.
Sadly, as it is now, we are left with relying on essentially locating the proverbial "needle in a haystack" with regard to locating the FDR. Another example is the case with AF447 [1]. Although the FDR was recovered, it was not until nearly 2 years after the incident.
My heart goes out to those that lost loved ones. Not having closure is an extremely painful and difficult process to endure.
[1] https://en.wikipedia.org/wiki/Air_France_Flight_447