Probably so many died because it was a small boat on a big lake. They were from a senior citizen group and that makes your reflexes slower. No life jackets seen on any of the pictures. And it is cold up there. By the end of August leaves are changing at least in the Central Adirondacks where we love to go.
Sounds like a bigger boat got so close as to make a huge wave that capsized this boat.
I was on a tour boat there last year - double decker - i.e. top heavy. if you are inside a capsized boat with the water rushing in - I sort of remember white life rings on white walls, and not one for everyone. They don't plan on capsizing.
There was a tour boat that turned turtle in Baltimore harbor a couple years ago.