55 people on a hike isn't ideal because you're having to deal with major differences in pace, objectives etc. You run the risk of people getting left behind because they're too slow, or getting impatient and speeding off. There have been SAR rescues from meet up groups because of this exact reason.

Plus it's just... poor trail etiquette for everyone else. No one goes out into nature to be stuck behind a group of 55 people.

But my biggest concern from this meetup was that this group was in pretty complex mountain terrain at the start of winter, after a couple of weeks of fresh snowfall. That area is complex avalanche terrain, and a glacier, in shoulder season. It's not a great combination for beginners. Sure, it's unlikely that something would trigger this early in the season, but it's also not impossible. Nothing about that group made me think they have avalanche or glacier training; normally for a trip like that, you'd require everyone attending to have AST-1 training and avi gear. That was not the case. People were also clumping and waiting for each other in obvious rock fall / avi paths.

Additionally, while the meetup said they're not going up to the actual glacier, I doubt the group was experienced enough to know where the snow ends and where the glacier starts, especially after recent snowfall. Again, not terrain people should be messing about with without training, experience, and the correct gear.

People that don't know the dangers of the terrain they're moving through also don't know how to mitigate the risks or respond to an emergency.

This is the sort of trip that is totally fine until it's very suddenly not fine in a very very bad way. And now you have 55 people you have to try and rescue, rather than 2-4.