While no defender of FR's mangement style, I do think a rational look at this event is worthwhile. Based on what we think we know, they all seem to have abandoned the MAD approach around 8000' so they would be about 500kg or so above div fuel. Into a hold to review the prognosis, and decision made to divert. Reasonable?
What is crucial now is when LAN declared the MAYDAY - as I have said before, there will inevitably be a 'ripple' effect on other a/c inbound to VLC on diversion once this happens, since they will become number 2+ and will be seeing 'Reserve' or less on landing on the FMC. Ipso Facto, and correctly, a MAYDAY call follows for the first FR a/c. Put yourself in the cockpit of the second FR a/c. What would you see on your FMC, and expect? Off goes your MAYDAY. Reasonable?
In aviation we have never planned to take 'extra' fuel for a div into a field just in case an emergency is in progress.
It may not have happened this way, but think about it - before you condemn out of hand the FR Captains' fuel decisions.