Another 'one more thing'.......
Flight crossed some fairly high terrain with a strong crossing jet stream at FL250. You know what that could mean. (Bumpy).
Anyone ever travel in a car with a back seat full of kids and one of them starts barfing? Can you imagine a close full cabin full of kids that started barfing? And how easily that smell/sight gets contagious?
Pilot goes on oxygen to stave off contagious smell, and requests divert. With descent as well, thought is to get on ground ASAP. Butte was closer, plates were already out, it made sense to go there first. Can you imagine 25 minutes of that going on?
Who knows what kind of shape you or I would be in and try to fly/communicate/land.....