Around 10 years ago, Internet historians discovered that the little-appreciated trebuchet (depicted bottom right) could launch a 90kg projectile in excess of 300m. Prior to this discovery much of the Internet’s medieval siege engine enthusiast community had presumed such a feat impossible due to its preoccupation with the catapult (a popular medieval siege engine [depicted top right]). This sensational discovery launched the previously poorly-regarded siege engine into the limelight of popular internet culture, much as a trebuchet might launch a 90kg payload into a fortification at a distance of ~300m.
What?
Before “the Internet historians” there was very clear and obvious evidence to the superiority of the trebuchet over the onager, mainly because the former completely supplanted the latter by the 6th century AD.
The onager (or catapult as you’re referring to it here) was invented in the 4th century.