This demonstration illustrates the fact that the vertical and horizontal motion of a projectile motion are independent of each other.
The coins were launched with the same initial vertical velocity of zero, but different horizontal velocities. Since the vertical motion is totally determined by the initial vertical velocity, all the coins drop vertically at the same rate, and land at the same time. The horizontal velocity determines how fast the coin moves forward. Since they land at the same time, the coin with the highest horizontal velocity lands furthest away.
How does the “launcher” work?
Basically, different parts of the ruler have the same angular velocity but different linear velocity (v=rω). Upon collision, the coins are thus launched at speeds proportional to the distance away from the pivot. In the video, the furthest coin is about 2 times away from the pivot as the nearest coin. So the furthest coin was launched at about 2 times initial speed as the nearest, resulting in it landing about 2 times as far as the nearest coin.