After a quick skim, my verdict would be dehydration more than just the regurgitation. Any kind of stress to a snake causes dehydration. In this case it would be the move being the big stress factor. Then the regurgitation which is a major factor for water loss. Plus the heat increasing the metabolism of the snakes and making them use up more water in their bodies than norm. All those three seem like a deadly combination.
I now I should have said this earlier though, but sorry to hear about your unfortunate loss. We all learn. Sometimes we learn the hard way. But then again , you know that the lessons learnt the hard way are almost never forgotten.
The Herp Room
"The day I tried to live, I wallowed in the blood and mud with all the other pigs" - C. Cornell