The smart bombs are simmply more effective. You do - after all - have specific targets you want to kill. Missing a “tent” by 200 feet that holds the meeting you want destroyed between ISIS leaders does nothing. WWII we were happy to get 20% of the bombs within 5 miles of the target - a factory or oil refinery or train depot. Forget bridges or submarine pens or tunnels. Only the specially-trained - and very few - Tallboy bombardiers could get close to kill those targets.
Now, any pilot can get every one with 90% success the first time. Don’t have to fly subsequent missions to try and miss the same target again.
B2 bomber can drop 80 500lb GPS guided bombs in one bombing run. All independently targetted.