Can three take on overwhelming numbers and win?
Here is a video where some fencers did just that.
I've done that on a smaller scale so I feel qualified to comment on it.
Why did the three masters do so well? They did everything right.
First, they never fought all 50 at once. The first thing they did was run. After that they used natural features (the staircase) to break up the attackers. They also flanked the group so that they blocked each other. For the most part, none of the masters faced more than 2 or 3 attackers at once.
All of that takes its toll. By the five minute mark the masters have changed tactics. The attackers' numbers have been reduced and they have broken into smaller groups. The masters start using distraction. One engages a group and a second master attacks from the side. In another case, the master points out one attacker then attacks the man beside him.
The masters also use some defensive tactics. The object is to burst a balloon on each fencer's chest. The attackers face the masters, exposing their balloons but the masters often turn away, shielding their balloons with their bodies.
Eventually exhaustion and sheer luck take their toll on the masters.
The moral here is that a skilled swordsman can take on multiple attackers and win if he uses the right strategy and if he can dispatch them before he runs out of energy.