There is no evidence to indicate that the family knew that being forced to put their beloved pet in his carrier in the overhead locker would prove fatal to him.
They probably thought that he would have been uncomfortable, but if they'd had any idea of the risk to his life, they would surely have put up a stronger argument - although that's pretty risky on UA with its record of forcible removals.
That picture of the deceased puppy with his little paw raised in a final pathetic struggle to escape from his incarceration is truly heartbreaking. French Bulldogs suffer separation anxiety more than other breeds and the distress this poor animal suffered was truly appalling.
Maggie Gremminger did a good job in publicising this event to the media.