I have seen nothing that even mentions whether or not this party was "lite," heavy, or in between.
I can't find the article that said that.  I thought it was The Olympian, but...
The articles say he had a bivy bag.  Not a sleeping bag and a bivy bag, just a bivy bag.  Let me guess:  he was wearing the clothes he sweated up the mountain in, then climbed into the bivy and ...
That's at 13,600 feet, temp. of ~5ºF in a 50 mph wind, on snow. Translation: 24º below zero!
He had gotten away with it before, and assumed he would get away with it again is probably closer to the truth.
I live between these two d**ned mountains, Rainier and Hood.  If it isn't some dorks climbing in winter with minimal gear, it's others climbing on a 'nice June day'.
"Experienced and well-equipped" -- yeah, aren't they all?
Sue