People, especially Bochurim, don’t know how much to take. They take a drink and don’t feel anything different, so they take another, and another. Then it all hits at once. Perhaps, if more people would drink, the Bochurim wouldn’t have to figure this out on their own. Instead of yelling at them, they should be shown, or told, what to do.
If you take a little, it makes you able, and willing, to dance without regard to tiredness and anything else that weighs you down.
Dancing on Simchas Torah is not a product of everybody being moved to dance. We know that we should dance, for the Simchas Hatorah, and we do. That creates the Simcha, which we are making for the Torah. When you drink, you are creating more Simcha.