I think there's a good argument that a "fall" happened. Only a decade after the "golden age" of detective novels, you hace a situation where a lot of once best-selling author's are no longer being published.

But like you point out, there's been a zillion other "rises" too. Maybe a more acurate but much longer article would be "the rise and fall and rise and fall and rise [...] of the British detective novel"

Exactly this.