I’ll take a wild guess: They escorted the chatan to shul for his aufruf that morning and got a little overheated. So they loosened their ties, and opened their collars. Loosening the tie pulls up the ends (remember this is a guess), and if they loosened the knot that would make it look fuller.
guess number two: Someone in their crowd heard that a full Windsor knot is more formal. So they all decided to wear it. Now, by it’s nature this knot uses more material in the knot, so less is left for the ends. Hence, the short-looking ties. Also, a full windsor should have a spread collar shirt, and since the guys didn’t have one, they opened their collars to accomodate the wider knot. They also wore their loudest ties to show off their knots.
I might as well bring up the point that I think some people don’t hold by this kind of knot on Shabbos, considering it more of a permanent knot.