It was the independent suspension that was added to give the Ford M-151s more mobility. That, and the weapons got bigger and heavier (TOW, etc.).
Yeah, a really dangerous design. There initially were no mechanical stops to keep the individual wheels from pivoting under the vehicle. This resulted and “snap rolls” with no warning other than the ground hitting your helmet.
An example of well-meaning engineers with no understanding of the operational requirements and realities of a system. As usual, the military doesn’t do a good job of operational requirements definition.
I speak as a retired Army Officer and retired Systems Architect.