Well, what "loaded them up" and why, we might never know.
For what's clear is - derived from the tansponder data - that they where not established, that they where high and fast, that they suddenly lost speed and that they fell near-stall nearly out of the skies.
Well, it really doesn't need much imagination to come to the theory I'm promoting for a long time and is constantly dismissed by nearly everyone here.
But Danny is correct by stating that most people have little knowledge about phyisical laws in aviation. One of these is the powerful force of two CFMs running from idle to full power within seconds: It's a huge nose-up-momentum, that can put your aircraft immediatly into an uncontrollable situation, even if you were not near stall before. This momentum is so strong that the books say don't use it in stall recovery (I don't know the Boeing books but at least the Airbus books say it, and I don't think that those two aircraft are very different in this very behaviour).
So if you watch the data from the transponder and interprete it with the little facts we have, it really doesn't need a lot of imagination to come to the conclusion I came to. I'm pretty convinced that there is no other solution than the obvious...
Keep discovering
Dani