In the interest of not criticising without offering an alternative...
Kruge actually was a agent of the Empire and fully transmitted all the Genesis data (protomatter included) before encountering the Enterprise.
Part of Praxis (with it's readily available energy) was turned into a secret lab to develop this new weapon. TPTB wanted a way of delivering the effect across multiple star systems at high warp speed so easily taking out an enemy empire quickly.
Scientists warned against risks but were overuled.
Pushed the experiment, far too far, one day, and it rushed out at high warp speed, decimating Praxis and the rest of the Klingon home system in milliseconds, then raced outward, decimating the Empire in all directions.
Klingons ask for Fed help to stop the wave (an explosion just caused by experimental energy production, you understand.). Feds soon recognise it is Genesis but assist anyway.
Effect finally reaches its end and fizzles out but most of the Empire is gone. Only Klingons left are frontier ship crews and outpost commanders ("Warriors" all).
And so we are left with TNG style Klingons in command......