I suppose we will never know what the exact reason of these failures was. It is certainly frustrating to have camera failures in any trip, let alone in a a trip like this, to such a wonderful place. Personally, whenever I move between two different environments in terms of humidity and/or temperature, I try to avoid condensation by letting the camera adjust to the different condition.
For instance, I once went to Moscow in the winter with the old EOS 30V (not much weather proofing on that one...), and I used it under very low temperatures. Whenever I had to go from outside to inside, I would put the camera in my bag, and let it warm up inside the bag for at least one hour.
When I have to go from air-con to hot and humid outside, I try to leave the camera outside, inside the bag, for 1 to 2 hours, so that it can warm up, and avoid condensation.