Easy question, cokecan. It was always going to be agile from the earliest UK and German requirements way back in the 70s. The lessons about high wing loaders were still fresh in the mind from Vietnam and requirements for new fighter designs were developed accordingly.
The fundamentals in the Typhoon's design pretty much demonstrate that - delta wing, canards, high thrust to weight, excellent pilot viz, etc. It just took an awfully long time to get there because of the difficulties of getting four nations (well, five actually) to agree to anything.
Oh, and it didn't become clear that Tornado couldn't cut the fighter mustard, it was never supposed to or expected to. It was always an interceptor.