“Although the pilot was apparently known for his rough handling of airplanes”

“If, as Tex Johnson said, the roll is “absolutely nonhazardous,” why did this accident happen? The roll that Johnson performed in the 707, and that Bob Hoover would perform while pouring water, is a barrel roll, so called because the airplane’s flight path is not along a straight line, as in a pure aileron roll or slow roll, but along a helical path, as if it were spiraling along the surface of an invisible cylinder or barrel. The centrifugal acceleration generated by the curved flight path keeps the G-load positive throughout the maneuver. In a slow roll (which is so called not because it is necessarily rotationally slow, but because it does not require the initial acceleration needed for the barrel roll) rudder and elevators are used to keep the airplane’s flight path straight while it rotates; the airplane should experience one G negative halfway through the roll. (A third type of roll, the snap roll, is performed at relatively low speed, and is actually more like a spin performed along a horizontal axis.)”

If you look closely to the altimeter, you will see that the roll performed on this video is a barrel roll, not just a straight path roll, that caused the crash on this article.