I think you will find that a stick pusher was part of the Trident design as early as 1964, some 8 years before the accident in Staines!
The Trident was a rear engined, "T" tail design which is subject to deep stalling, where the tailplane and engines can have their airflow blanketed by the wings, resulting in loss of elevator authority, rudder authority and engine flame out. Much higher levels of stall prevention would obviously need to be applied at the design and certification stage. Some conventional aircraft with undesirable stall characteristics have to have additional protections fitted, the SA227 a twin engined turbo prop with a max TOW of 6804kgs requires a stick shaker and a stick pusher which aren't normally required in aircraft of this class.
Boeing may have decided to increase the level of protection on the MAX series due to undesirable behaviour exhibited during flight testing, but may not have been keen to publicise the fact that their design had poor stalling qualities. Had Boeing been more upfront and required additional training and understanding of the system from pilots moving onto the type this may not have happened.
Most aircraft have their little quirks and as long as they are known about and understood by the pilots and engineers they can be mitigated.