Unfortunately, the ejection seat wasn't the zero-zero type that can be pulled at zero altitude and zero forward speed and still deliver sufficient height for a safe outcome. Those type seats have steerable solid rocket boosters with gyroscopic controls. They automatically point the seat to vertical flight, and the rocket motor increases the seat altitude enough to allow a successful parachute deployment even if the aircraft is stationary on a runway.
Instead, the older generation seat in the CT-114 fires an explosive round to separate it from the aircraft (the sound is obvious in the video), and the trajectory is fixed. It pushes the seat almost straight up from the fuselage centerline.
At the moment of ejection, the aircraft was in a high speed steep dive approaching the ground, and as a result the seats were propelled almost horizontally with a significant downward vector. There was not enough time to get a good canopy, and both of the crew hit hard.